diff --git a/src/Core/ObjectsContext.h b/src/Core/ObjectsContext.h
index a548d42..4264e61 100644
--- a/src/Core/ObjectsContext.h
+++ b/src/Core/ObjectsContext.h
@@ -20,13 +20,13 @@ public:
      * @brief Adds an object to the context.
      * @param obj Pointer to the object to add.
      */
-    void AddObject(Object* obj);
+    virtual void AddObject(Object* obj);
 
     /**
      * @brief Removes an object from the context.
      * @param obj Pointer to the object to remove.
      */
-    void RemoveObject(Object* obj);
+    virtual void RemoveObject(Object* obj);
 
     /**
      * @brief Clears all objects from the context.
diff --git a/src/Math/Assembly.cpp b/src/Math/Assembly.cpp
new file mode 100644
index 0000000..1966fdd
--- /dev/null
+++ b/src/Math/Assembly.cpp
@@ -0,0 +1,146 @@
+/*//////////////////////////////////////////////////////////////////////////////
+// CMT Cosmic Muon Tomography project //////////////////////////////////////////
+////////////////////////////////////////////////////////////////////////////////
+
+  Copyright (c) 2014, Universita' degli Studi di Padova, INFN sez. di Padova
+  All rights reserved
+
+  Authors: Andrea Rigoni Garola < andrea.rigoni@pd.infn.it >
+
+//////////////////////////////////////////////////////////////////////////////*/
+
+#include "Math/Assembly.h"
+#include "Math/ContainerBox.h"
+#include "Math/Cylinder.h"
+
+#include <limits>
+#include <algorithm>
+#include <cstring>
+
+namespace uLib {
+
+Assembly::Assembly()
+    : ObjectsContext(),
+      AffineTransform(),
+      m_BBoxMin(Vector3f::Zero()),
+      m_BBoxMax(Vector3f::Zero()),
+      m_ShowBoundingBox(false),
+      m_GroupSelection(true) {}
+
+Assembly::Assembly(const Assembly &copy)
+    : ObjectsContext(copy),
+      AffineTransform(copy),
+      m_BBoxMin(copy.m_BBoxMin),
+      m_BBoxMax(copy.m_BBoxMax),
+      m_ShowBoundingBox(copy.m_ShowBoundingBox),
+      m_GroupSelection(copy.m_GroupSelection) {}
+
+Assembly::~Assembly() {}
+
+void Assembly::AddObject(Object *obj) {
+    if (auto *at = dynamic_cast<AffineTransform *>(obj)) {
+        at->SetParent(this);
+    }
+    ObjectsContext::AddObject(obj);
+}
+
+void Assembly::RemoveObject(Object *obj) {
+    if (auto *at = dynamic_cast<AffineTransform *>(obj)) {
+        if (at->GetParent() == this)
+            at->SetParent(nullptr);
+    }
+    ObjectsContext::RemoveObject(obj);
+}
+
+void Assembly::ComputeBoundingBox() {
+    const auto &objects = this->GetObjects();
+    if (objects.empty()) {
+        m_BBoxMin = Vector3f::Zero();
+        m_BBoxMax = Vector3f::Zero();
+        return;
+    }
+
+    float inf = std::numeric_limits<float>::max();
+    m_BBoxMin = Vector3f(inf, inf, inf);
+    m_BBoxMax = Vector3f(-inf, -inf, -inf);
+
+    Matrix4f invAsm = this->GetWorldMatrix().inverse();
+
+    for (Object *obj : objects) {
+        if (auto *box = dynamic_cast<ContainerBox *>(obj)) {
+            // ContainerBox: wm is matrix from unit cube [0,1] to assembly base
+            Matrix4f m = invAsm * box->GetWorldMatrix();
+            for (int i = 0; i < 8; ++i) {
+                float x = (i & 1) ? 1.0f : 0.0f;
+                float y = (i & 2) ? 1.0f : 0.0f;
+                float z = (i & 4) ? 1.0f : 0.0f;
+                Vector4f corner = m * Vector4f(x, y, z, 1.0f);
+                for (int a = 0; a < 3; ++a) {
+                    m_BBoxMin(a) = std::min(m_BBoxMin(a), corner(a));
+                    m_BBoxMax(a) = std::max(m_BBoxMax(a), corner(a));
+                }
+            }
+        } else if (auto *cyl = dynamic_cast<Cylinder *>(obj)) {
+            // Cylinder: centered [-1, 1] radial, [-0.5, 0.5] height
+            Matrix4f m = invAsm * cyl->GetWorldMatrix();
+            for (int i = 0; i < 8; ++i) {
+                float x = (i & 1) ? 1.0f : -1.0f;
+                float y = (i & 2) ? 0.5f : -0.5f;
+                float z = (i & 4) ? 1.0f : -1.0f;
+                Vector4f corner = m * Vector4f(x, y, z, 1.0f);
+                for (int a = 0; a < 3; ++a) {
+                    m_BBoxMin(a) = std::min(m_BBoxMin(a), corner(a));
+                    m_BBoxMax(a) = std::max(m_BBoxMax(a), corner(a));
+                }
+            }
+        } else if (auto *subAsm = dynamic_cast<Assembly *>(obj)) {
+            // Recursive AABB for nested assemblies
+            subAsm->ComputeBoundingBox();
+            Vector3f subMin, subMax;
+            subAsm->GetBoundingBox(subMin, subMax);
+            Matrix4f m = invAsm * subAsm->GetWorldMatrix();
+            for (int i = 0; i < 8; ++i) {
+                float x = (i & 1) ? subMax(0) : subMin(0);
+                float y = (i & 2) ? subMax(1) : subMin(1);
+                float z = (i & 4) ? subMax(2) : subMin(2);
+                Vector4f corner = m * Vector4f(x, y, z, 1.0f);
+                for (int a = 0; a < 3; ++a) {
+                    m_BBoxMin(a) = std::min(m_BBoxMin(a), corner(a));
+                    m_BBoxMax(a) = std::max(m_BBoxMax(a), corner(a));
+                }
+            }
+        }
+    }
+}
+
+void Assembly::GetBoundingBox(Vector3f &bbMin, Vector3f &bbMax) const {
+    bbMin = m_BBoxMin;
+    bbMax = m_BBoxMax;
+}
+
+ContainerBox Assembly::GetBoundingBoxAsContainer() const {
+    ContainerBox bb;
+    Vector3f size = m_BBoxMax - m_BBoxMin;
+    bb.SetSize(size);
+    bb.SetPosition(m_BBoxMin);
+    return bb;
+}
+
+void Assembly::SetShowBoundingBox(bool show) {
+    m_ShowBoundingBox = show;
+    this->Updated();
+}
+
+bool Assembly::GetShowBoundingBox() const {
+    return m_ShowBoundingBox;
+}
+
+void Assembly::SetGroupSelection(bool group) {
+    m_GroupSelection = group;
+}
+
+bool Assembly::GetGroupSelection() const {
+    return m_GroupSelection;
+}
+
+} // namespace uLib
diff --git a/src/Math/Assembly.h b/src/Math/Assembly.h
new file mode 100644
index 0000000..7440062
--- /dev/null
+++ b/src/Math/Assembly.h
@@ -0,0 +1,109 @@
+/*//////////////////////////////////////////////////////////////////////////////
+// CMT Cosmic Muon Tomography project //////////////////////////////////////////
+////////////////////////////////////////////////////////////////////////////////
+
+  Copyright (c) 2014, Universita' degli Studi di Padova, INFN sez. di Padova
+  All rights reserved
+
+  Authors: Andrea Rigoni Garola < andrea.rigoni@pd.infn.it >
+
+  ------------------------------------------------------------------
+  This library is free software;  you  can  redistribute  it  and/or
+  modify it  under the  terms  of  the  GNU  Lesser  General  Public
+  License as published  by  the  Free  Software  Foundation;  either
+  version 3.0 of the License, or (at your option) any later version.
+
+  This library is  distributed in  the hope that it will  be useful,
+  but  WITHOUT ANY WARRANTY;  without  even  the implied warranty of
+  MERCHANTABILITY  or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of  the GNU Lesser General  Public
+  License along with this library.
+
+//////////////////////////////////////////////////////////////////////////////*/
+
+#ifndef U_ASSEMBLY_H
+#define U_ASSEMBLY_H
+
+#include "Core/ObjectsContext.h"
+#include "Math/ContainerBox.h"
+#include "Math/Transform.h"
+
+namespace uLib {
+
+/**
+ * @brief Assembly groups geometric objects (ContainerBox, Cylinder, etc.)
+ * under a common transformation.
+ *
+ * Assembly derives from ObjectsContext so objects can be added/removed
+ * dynamically. It also inherits AffineTransform to provide a group-level
+ * transformation that is applied on top of each child's own transform.
+ *
+ * A bounding box is automatically computed from all contained objects and
+ * can be queried or shown/hidden through the VTK puppet.
+ */
+class Assembly : public ObjectsContext, public AffineTransform {
+public:
+    virtual const char *GetClassName() const override { return "Assembly"; }
+
+    Assembly();
+    Assembly(const Assembly &copy);
+    virtual ~Assembly();
+
+    virtual void AddObject(Object* obj) override;
+    virtual void RemoveObject(Object* obj) override;
+
+    /**
+     * @brief Recomputes the axis-aligned bounding box enclosing all children.
+     * Stores the result internally.
+     */
+    void ComputeBoundingBox();
+
+    /**
+     * @brief Returns the bounding box as min/max corners (in assembly-local
+     * coordinates).
+     */
+    void GetBoundingBox(Vector3f &bbMin, Vector3f &bbMax) const;
+
+    /**
+     * @brief Returns the bounding box as a ContainerBox (positioned
+     * at bbMin, sized bbMax-bbMin, parented to this transform).
+     */
+    ContainerBox GetBoundingBoxAsContainer() const;
+
+    /**
+     * @brief Controls whether the bounding box wireframe should be shown
+     * in the viewer (used by the VTK puppet).
+     */
+    void SetShowBoundingBox(bool show);
+    bool GetShowBoundingBox() const;
+    
+    /**
+     * @brief Controls selection behavior.
+     * If true (default), clicking any child within the assembly will select 
+     * the assembly itself. If false, individual children can be picked.
+     */
+    void SetGroupSelection(bool group);
+    bool GetGroupSelection() const;
+
+signals:
+    virtual void Updated() override {
+        if (m_InUpdated) return;  // break signal recursion
+        m_InUpdated = true;
+        this->ComputeBoundingBox();
+        ULIB_SIGNAL_EMIT(Assembly::Updated);
+        m_InUpdated = false;
+    }
+
+private:
+    Vector3f m_BBoxMin;
+    Vector3f m_BBoxMax;
+    bool     m_ShowBoundingBox;
+    bool     m_GroupSelection;
+    bool     m_InUpdated = false;
+};
+
+} // namespace uLib
+
+#endif // U_ASSEMBLY_H
diff --git a/src/Math/CMakeLists.txt b/src/Math/CMakeLists.txt
index 3121b33..a14a1bc 100644
--- a/src/Math/CMakeLists.txt
+++ b/src/Math/CMakeLists.txt
@@ -1,6 +1,7 @@
 
 set(HEADERS ContainerBox.h
             Cylinder.h
+            Assembly.h
             Dense.h
             Geometry.h
             Transform.h
@@ -33,6 +34,7 @@ set(SOURCES VoxRaytracer.cpp
             VoxImage.cpp
             TriangleMesh.cpp
             QuadMesh.cpp
+            Assembly.cpp
             Dense.cpp
             Structured2DGrid.cpp
             Structured4DGrid.cpp
diff --git a/src/Math/Transform.h b/src/Math/Transform.h
index 232ed75..73cfacd 100644
--- a/src/Math/Transform.h
+++ b/src/Math/Transform.h
@@ -69,6 +69,8 @@ public:
         m_Parent(NULL)
     {}
 
+    virtual ~AffineTransform() {}
+
     AffineTransform(AffineTransform *parent) :
         m_T(Matrix4f::Identity()),
         m_Parent(parent)
diff --git a/src/Vtk/Math/CMakeLists.txt b/src/Vtk/Math/CMakeLists.txt
index c722d94..0dbe4c3 100644
--- a/src/Vtk/Math/CMakeLists.txt
+++ b/src/Vtk/Math/CMakeLists.txt
@@ -10,6 +10,7 @@ set(MATH_SOURCES
     ${CMAKE_CURRENT_SOURCE_DIR}/vtkVoxImage.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/vtkContainerBox.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/vtkCylinder.cpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/vtkAssembly.cpp
     PARENT_SCOPE)
 
 set(MATH_HEADERS
@@ -20,6 +21,7 @@ set(MATH_HEADERS
     ${CMAKE_CURRENT_SOURCE_DIR}/vtkVoxImage.h
     ${CMAKE_CURRENT_SOURCE_DIR}/vtkContainerBox.h
     ${CMAKE_CURRENT_SOURCE_DIR}/vtkCylinder.h
+    ${CMAKE_CURRENT_SOURCE_DIR}/vtkAssembly.h
     PARENT_SCOPE)
 
 if(BUILD_TESTING)
diff --git a/src/Vtk/Math/testing/CMakeLists.txt b/src/Vtk/Math/testing/CMakeLists.txt
index 04eaec3..a0a6edf 100644
--- a/src/Vtk/Math/testing/CMakeLists.txt
+++ b/src/Vtk/Math/testing/CMakeLists.txt
@@ -7,6 +7,7 @@ set(TESTS
     vtkVoxImageInteractiveTest
     vtkContainerBoxTest
     vtkContainerBoxTest2
+    vtkAssemblyTest
 )
 
 set(LIBRARIES
diff --git a/src/Vtk/Math/testing/vtkAssemblyTest.cpp b/src/Vtk/Math/testing/vtkAssemblyTest.cpp
index 713deb2..77bffb3 100644
--- a/src/Vtk/Math/testing/vtkAssemblyTest.cpp
+++ b/src/Vtk/Math/testing/vtkAssemblyTest.cpp
@@ -1,109 +1,104 @@
 /*//////////////////////////////////////////////////////////////////////////////
 // CMT Cosmic Muon Tomography project //////////////////////////////////////////
 ////////////////////////////////////////////////////////////////////////////////
-// Copyright (c) 2014, Universita' degli Studi di Padova, INFN sez. di Padova
-// All rights reserved
+
+  Copyright (c) 2014, Universita' degli Studi di Padova, INFN sez. di Padova
+  All rights reserved
+
+  Authors: Andrea Rigoni Garola < andrea.rigoni@pd.infn.it >
+
 //////////////////////////////////////////////////////////////////////////////*/
 
-#include "Vtk/uLibVtkViewer.h"
-#include "Vtk/Math/vtkAssembly.h"
-#include "Vtk/Math/vtkCylinder.h"
-#include "Vtk/Math/vtkContainerBox.h"
 #include "Math/Assembly.h"
-#include "Math/Cylinder.h"
 #include "Math/ContainerBox.h"
+#include "Math/Cylinder.h"
+#include "Vtk/Math/vtkAssembly.h"
+#include "Vtk/vtkObjectsContext.h"
+#include "Vtk/uLibVtkViewer.h"
 #include "Math/Units.h"
 
+#include <vtkActor.h>
+#include <vtkProperty.h>
+#include <vtkPropCollection.h>
+
 #include <iostream>
 
 using namespace uLib;
 
-/**
- * @brief This test verifies that uLib::Vtk::Assembly correctly visualizes a collection 
- * of objects and that transformations applied to the assembly are propagated to its children.
- * It also checks that the assembly appears as a bounding box of its contents.
- */
-int main() {
-    std::cout << "Starting vtkAssemblyTest..." << std::endl;
+int main(int argc, char **argv) {
+    bool interactive = (argc > 1 && std::string(argv[1]) == "-i");
 
-    // 1. Setup Core Geometry
-    std::cout << "  - Creating core Assembly..." << std::endl;
-    uLib::Assembly* core_assembly = new uLib::Assembly();
-    core_assembly->SetInstanceName("MainAssembly");
+    // ---- 1. Build model objects ----
+    ContainerBox box1;
+    box1.Scale(Vector3f(1_m, 2_m, 0.5_m));
+    box1.SetPosition(Vector3f(0, 0, 0));
 
-    // Add a box
-    std::cout << "  - Adding ChildBox (Red)..." << std::endl;
-    ContainerBox* box = new ContainerBox();
-    box->SetInstanceName("ChildBox");
-    box->Translate(Vector3f(1.0, 0, 0));
-    core_assembly->AddObject(box);
+    ContainerBox box2;
+    box2.Scale(Vector3f(0.5_m, 0.5_m, 3_m));
+    box2.SetPosition(Vector3f(2_m, 0, 0));
 
-    // Add a cylinder
-    // std::cout << "  - Adding ChildCylinder (Blue)..." << std::endl;
-    // Cylinder* cyl = new Cylinder(0.5, 2.0);
-    // cyl->SetInstanceName("ChildCylinder");
-    // cyl->Translate(Vector3f(-2.0, 0, 0));
-    // core_assembly->AddObject(cyl);
+    Cylinder cyl(0.3_m, 1.5_m, 1);
+    cyl.SetPosition(Vector3f(0, 3_m, 0));
 
-    std::cout << "  - Adding another box (Green)..." << std::endl;
-    ContainerBox* box2 = new ContainerBox();
-    box2->Scale(Vector3f(1.0, 1.0, 2.0));
-    box2->SetInstanceName("ChildBox2");
-    box2->Translate(Vector3f(0, 0, 1.0));
-    core_assembly->AddObject(box2);
+    // ---- 2. Create an Assembly and add objects ----
+    Assembly assembly;
+    assembly.AddObject(&box1);
+    assembly.AddObject(&box2);
+    assembly.AddObject(&cyl);
+    assembly.SetShowBoundingBox(true);
 
-    // 2. Setup VTK Representation
-    std::cout << "  - Creating VTK Assembly representation..." << std::endl;
-    Vtk::Assembly vtk_assembly(core_assembly);
-    
-    // Find and colorized the children puppets
-    Vtk::Puppet* p_box = vtk_assembly.GetPuppet(box);
-    if (p_box) {
-        p_box->SetColor(1.0, 0.0, 0.0); // Red
-    } else {
-        std::cerr << "Warning: Could not find puppet for box!" << std::endl;
-    }
+    // ---- 3. Apply a group transform ----
+    assembly.SetPosition(Vector3f(1_m, 1_m, 0));
 
-    // Vtk::Puppet* p_cyl = vtk_assembly.GetPuppet(cyl);
-    // if (p_cyl) {
-    //     p_cyl->SetColor(0.0, 0.0, 1.0); // Blue
-    // } else {
-    //     std::cerr << "Warning: Could not find puppet for cylinder!" << std::endl;
-    // }
-
-    Vtk::Puppet* p_box2 = vtk_assembly.GetPuppet(box2);
-    if (p_box2) {
-        p_box2->SetColor(0.0, 1.0, 0.0); // Green
-    } else {
-        std::cerr << "Warning: Could not find puppet for box2!" << std::endl;
-    }
-
-    // 3. Test Transformation Propagation
-    std::cout << "  - Rotating Assembly 45 degrees around Z..." << std::endl;
-    core_assembly->Rotate(45.0_deg, Vector3f::UnitZ());
-    
-    std::cout << "  - Translating Assembly up (+Y)..." << std::endl;
-    core_assembly->Translate(Vector3f(0, 2.0, 0));
-
-    // Notify all puppets of the change
-    core_assembly->Updated();
-
-    // 4. Run Visualization
-    std::cout << "Starting viewer (close to exit)..." << std::endl;
-    std::cout << "Expected: A white bounding box containing a red box and a blue cylinder, "
-              << "all rotated and translated as a group." << std::endl;
+    // ---- 5. Visualize (create puppets to set properties) ----
+    Vtk::Assembly vtkAsm(&assembly);
 
     Vtk::Viewer viewer;
-    viewer.AddPuppet(*p_box);
-    viewer.AddPuppet(*p_box2);
-    viewer.AddPuppet(vtk_assembly);
-    viewer.Start();
+    vtkAsm.AddToViewer(viewer); // This triggers puppet creation via ConnectRenderer which eventually calls Puppet::GetProp
+    
+    // Explicitly update to ensure puppets exist and are added to assemblies
+    vtkAsm.Update();
 
-    // Clean up
-    delete core_assembly;
-    delete box;
-    delete box2;
-    // delete cyl;
+    // Use the child context to find child puppets and set colors
+    if (auto* childCtx = vtkAsm.GetChildrenContext()) {
+        auto setProps = [](Vtk::Puppet* p, float r, float g, float b) {
+            if (!p) return;
+            vtkPropCollection* props = p->GetProps();
+            props->InitTraversal();
+            for (int i=0; i < props->GetNumberOfItems(); ++i) {
+                if (auto* actor = vtkActor::SafeDownCast(props->GetNextProp())) {
+                    actor->GetProperty()->SetColor(r, g, b);
+                    actor->GetProperty()->SetRepresentationToSurface();
+                    actor->GetProperty()->SetOpacity(0.5);
+                }
+            }
+        };
+
+        setProps(childCtx->GetPuppet(&box1), 1.0, 0.0, 0.0); // Red
+        setProps(childCtx->GetPuppet(&box2), 0.0, 1.0, 0.0); // Green
+        setProps(childCtx->GetPuppet(&cyl),  0.0, 0.0, 1.0); // Blue
+    }
+
+    std::cout << "Puppets in viewport: " << viewer.getPuppets().size() << " (Expected 4: 1 assembly + 3 children)" << std::endl;
+
+    // ---- 4. Query the bounding box for terminal output ----
+    Vector3f bbMin, bbMax;
+    assembly.GetBoundingBox(bbMin, bbMax);
+    std::cout << "Assembly bounding box:" << std::endl;
+    std::cout << "  min = " << bbMin.transpose() << std::endl;
+    std::cout << "  max = " << bbMax.transpose() << std::endl;
+
+    std::cout << "==================================================\n";
+    std::cout << " vtkAssemblyTest\n";
+    std::cout << " 2 boxes + 1 cylinder grouped in an assembly\n";
+    std::cout << "==================================================" << std::endl;
+
+    if (interactive) {
+        viewer.ZoomAuto();
+        viewer.Start();
+    } else {
+        std::cout << "Non-interactive test passed." << std::endl;
+    }
 
     return 0;
 }
diff --git a/src/Vtk/Math/vtkAssembly.cpp b/src/Vtk/Math/vtkAssembly.cpp
new file mode 100644
index 0000000..19a3fd7
--- /dev/null
+++ b/src/Vtk/Math/vtkAssembly.cpp
@@ -0,0 +1,210 @@
+/*//////////////////////////////////////////////////////////////////////////////
+// CMT Cosmic Muon Tomography project //////////////////////////////////////////
+////////////////////////////////////////////////////////////////////////////////
+
+  Copyright (c) 2014, Universita' degli Studi di Padova, INFN sez. di Padova
+  All rights reserved
+
+  Authors: Andrea Rigoni Garola < andrea.rigoni@pd.infn.it >
+
+//////////////////////////////////////////////////////////////////////////////*/
+
+#include "vtkAssembly.h"       // uLib::Vtk::Assembly
+#include "Vtk/vtkObjectsContext.h"
+#include "Math/vtkDense.h"
+
+#include <vtkAssembly.h>       // VTK library ::vtkAssembly
+#include <vtkActor.h>
+#include <vtkCubeSource.h>
+#include <vtkPolyDataMapper.h>
+#include <vtkProperty.h>
+#include <vtkMatrix4x4.h>
+#include <vtkPropCollection.h>
+#include <vtkNew.h>
+#include <vtkProp3D.h>
+#include <vtkPoints.h>
+#include <vtkCellArray.h>
+#include <vtkPolyData.h>
+
+namespace uLib {
+namespace Vtk {
+
+// ------------------------------------------------------------------ //
+Assembly::Assembly(uLib::Assembly *content)
+    : m_Content(content),
+      m_ChildContext(nullptr),
+      m_BBoxActor(nullptr),
+      m_VtkAsm(nullptr),
+      m_InUpdate(false),
+      m_BlockUpdate(false) {
+    this->InstallPipe();
+    if (m_Content) {
+        Object::connect(m_Content, &uLib::Assembly::Updated,
+                        this, &Assembly::contentUpdate);
+    }
+}
+
+Assembly::~Assembly() {
+    delete m_ChildContext;
+    if (m_BBoxActor)  m_BBoxActor->Delete();
+    if (m_VtkAsm)     m_VtkAsm->Delete();
+}
+
+// ------------------------------------------------------------------ //
+void Assembly::InstallPipe() {
+    // 1. Create the VTK library assembly that groups everything
+    m_VtkAsm = ::vtkAssembly::New();
+    this->SetProp(m_VtkAsm);
+
+    // 2. Create the bounding-box wireframe actor
+    vtkNew<vtkCubeSource> cube;
+    cube->SetBounds(0, 1, 0, 1, 0, 1);
+    cube->Update();
+
+    vtkNew<vtkPolyDataMapper> mapper;
+    mapper->SetInputConnection(cube->GetOutputPort());
+
+    m_BBoxActor = vtkActor::New();
+    m_BBoxActor->SetMapper(mapper);
+    m_BBoxActor->GetProperty()->SetRepresentationToWireframe();
+    m_BBoxActor->GetProperty()->SetColor(1.0, 0.85, 0.0);   // gold wireframe
+    m_BBoxActor->GetProperty()->SetLineWidth(1.5);
+    m_BBoxActor->GetProperty()->SetOpacity(0.6);
+    m_BBoxActor->SetVisibility(m_Content ? m_Content->GetShowBoundingBox() : false);
+
+    m_VtkAsm->AddPart(m_BBoxActor);
+
+    // 3. Build a child-objects context (auto-creates puppets for each child)
+    if (m_Content) {
+        m_ChildContext = new vtkObjectsContext(m_Content);
+        // The vtkObjectsContext's own prop is already a ::vtkAssembly;
+        // nest it inside ours so everything moves together.
+        if (auto *childProp = vtkProp3D::SafeDownCast(m_ChildContext->GetProp()))
+            m_VtkAsm->AddPart(childProp);
+    }
+
+    // 4. Apply initial transform
+    this->UpdateTransform();
+    this->UpdateBoundingBox();
+}
+
+// ------------------------------------------------------------------ //
+void Assembly::contentUpdate() {
+    if (m_InUpdate) return;
+    m_InUpdate = true;
+
+    this->UpdateTransform();
+    this->UpdateBoundingBox();
+    if (m_ChildContext)
+        m_ChildContext->Update();
+
+    m_BlockUpdate = true;
+    Puppet::Update();
+    m_InUpdate = false;
+}
+
+// ------------------------------------------------------------------ //
+void Assembly::Update() {
+    if (m_InUpdate) return;
+    if (!m_Content || !m_VtkAsm) return;
+
+    if (m_BlockUpdate) {
+        m_BlockUpdate = false;
+        return;
+    }
+
+    m_InUpdate = true;
+
+    // Pull VTK transform back into the uLib model
+    vtkMatrix4x4* vmat = m_VtkAsm->GetUserMatrix();
+    if (vmat) {
+        Matrix4f transform = VtkToMatrix4f(vmat);
+        m_Content->SetMatrix(transform);
+    }
+
+    this->UpdateBoundingBox();
+    if (m_ChildContext)
+        m_ChildContext->Update();
+
+    m_Content->Updated(); // Notify change in model
+
+    m_InUpdate = false;
+}
+
+// ------------------------------------------------------------------ //
+void Assembly::UpdateTransform() {
+    if (!m_Content || !m_VtkAsm) return;
+
+    Matrix4f mat = m_Content->GetMatrix();
+    vtkNew<vtkMatrix4x4> vmat;
+    Matrix4fToVtk(mat, vmat);
+    m_VtkAsm->SetUserMatrix(vmat);
+    m_VtkAsm->Modified();
+}
+
+// ------------------------------------------------------------------ //
+void Assembly::UpdateBoundingBox() {
+    if (!m_Content || !m_BBoxActor) return;
+
+    m_BBoxActor->SetVisibility(m_Content->GetShowBoundingBox());
+
+    Vector3f bbMin, bbMax;
+    m_Content->GetBoundingBox(bbMin, bbMax);
+
+    // Avoid degenerate boxes
+    Vector3f size = bbMax - bbMin;
+    if (size.norm() < 1e-6f) return;
+
+    // Rebuild the corner segments to match the AABB
+    vtkNew<vtkPoints> points;
+    vtkNew<vtkCellArray> lines;
+
+    float bounds[2][3] = {
+        {bbMin(0), bbMin(1), bbMin(2)},
+        {bbMax(0), bbMax(1), bbMax(2)}
+    };
+
+    // Corner segment length: 10% of dimension
+    float len[3] = {
+        (bbMax(0) - bbMin(0)) * 0.1f,
+        (bbMax(1) - bbMin(1)) * 0.1f,
+        (bbMax(2) - bbMin(2)) * 0.1f
+    };
+
+    for (int i = 0; i < 8; ++i) {
+        float p[3];
+        p[0] = bounds[(i & 1) ? 1 : 0][0];
+        p[1] = bounds[(i & 2) ? 1 : 0][1];
+        p[2] = bounds[(i & 4) ? 1 : 0][2];
+
+        for (int axis = 0; axis < 3; ++axis) {
+            float p2[3] = {p[0], p[1], p[2]};
+            float delta = (i & (1 << axis)) ? -len[axis] : len[axis];
+            p2[axis] += delta;
+
+            vtkIdType id1 = points->InsertNextPoint(p);
+            vtkIdType id2 = points->InsertNextPoint(p2);
+            lines->InsertNextCell(2);
+            lines->InsertCellPoint(id1);
+            lines->InsertCellPoint(id2);
+        }
+    }
+
+    vtkNew<vtkPolyData> poly;
+    poly->SetPoints(points);
+    poly->SetLines(lines);
+
+    vtkNew<vtkPolyDataMapper> mapper;
+    mapper->SetInputData(poly);
+
+    m_BBoxActor->SetMapper(mapper);
+    m_BBoxActor->Modified();
+}
+
+// ------------------------------------------------------------------ //
+vtkObjectsContext *Assembly::GetChildrenContext() const {
+    return m_ChildContext;
+}
+
+} // namespace Vtk
+} // namespace uLib
diff --git a/src/Vtk/Math/vtkAssembly.h b/src/Vtk/Math/vtkAssembly.h
new file mode 100644
index 0000000..297a9c0
--- /dev/null
+++ b/src/Vtk/Math/vtkAssembly.h
@@ -0,0 +1,71 @@
+/*//////////////////////////////////////////////////////////////////////////////
+// CMT Cosmic Muon Tomography project //////////////////////////////////////////
+////////////////////////////////////////////////////////////////////////////////
+
+  Copyright (c) 2014, Universita' degli Studi di Padova, INFN sez. di Padova
+  All rights reserved
+
+  Authors: Andrea Rigoni Garola < andrea.rigoni@pd.infn.it >
+
+//////////////////////////////////////////////////////////////////////////////*/
+
+#ifndef U_VTK_ASSEMBLY_H
+#define U_VTK_ASSEMBLY_H
+
+#include "Math/Assembly.h"
+#include "uLibVtkInterface.h"
+
+class vtkActor;
+class vtkAssembly;  // VTK library forward declaration (must be before namespace)
+
+namespace uLib {
+namespace Vtk {
+
+class vtkObjectsContext; // forward
+
+/**
+ * @brief VTK Puppet for visualizing uLib::Assembly.
+ *
+ * Manages a VTK assembly (vtkAssembly from the VTK library) that groups
+ * all child puppets and applies the Assembly's AffineTransform. It also
+ * renders an optional bounding box wireframe computed from the Assembly's AABB.
+ *
+ * @note This class is uLib::Vtk::Assembly. It internally uses
+ *       the VTK library class vtkAssembly for grouping, but the two
+ *       are distinct.
+ */
+class Assembly : public Puppet {
+public:
+    virtual const char *GetClassName() const override { return "Vtk.Assembly"; }
+
+    Assembly(uLib::Assembly *content);
+    virtual ~Assembly();
+
+    /** @brief Updates the VTK representation from the model (model→VTK). */
+    virtual void Update() override;
+
+    virtual uLib::Object* GetContent() const override { return (uLib::Object*)m_Content; }
+
+    /** @brief Called when the model signals an update (model→VTK push). */
+    void contentUpdate();
+
+    /** @brief Returns the puppet managing child objects. */
+    vtkObjectsContext *GetChildrenContext() const;
+
+private:
+    void UpdateTransform();
+    void UpdateBoundingBox();
+    void InstallPipe();
+
+    uLib::Assembly     *m_Content;
+    vtkObjectsContext  *m_ChildContext;
+    vtkActor           *m_BBoxActor;
+    ::vtkAssembly      *m_VtkAsm; // VTK library assembly — NOT this class
+    bool                m_InUpdate;    // re-entrancy guard
+    bool                m_BlockUpdate; // block feedback from contentUpdate→Update
+};
+
+} // namespace Vtk
+} // namespace uLib
+
+#endif // U_VTK_ASSEMBLY_H
diff --git a/src/Vtk/Math/vtkContainerBox.h b/src/Vtk/Math/vtkContainerBox.h
index 6656306..4b4bfd6 100644
--- a/src/Vtk/Math/vtkContainerBox.h
+++ b/src/Vtk/Math/vtkContainerBox.h
@@ -51,6 +51,8 @@ public:
 
   virtual void Update();
 
+  virtual uLib::Object* GetContent() const override { return (uLib::Object*)m_Content; }
+
 protected:
   virtual void InstallPipe();
 
diff --git a/src/Vtk/Math/vtkCylinder.cpp b/src/Vtk/Math/vtkCylinder.cpp
index e3e1e8a..d9f2741 100644
--- a/src/Vtk/Math/vtkCylinder.cpp
+++ b/src/Vtk/Math/vtkCylinder.cpp
@@ -25,6 +25,7 @@
 
 #include "Vtk/Math/vtkCylinder.h"
 #include <vtkActor.h>
+#include <vtkAssembly.h>
 #include <vtkCylinderSource.h>
 #include <vtkMatrix4x4.h>
 #include <vtkPolyDataMapper.h>
@@ -37,13 +38,14 @@ namespace uLib {
 namespace Vtk {
 
 vtkCylinder::vtkCylinder(vtkCylinder::Content *content)
-    : m_Actor(vtkActor::New()), m_Content(content) {
+    : m_Content(content), m_Actor(nullptr), m_VtkAsm(nullptr) {
   this->InstallPipe();
   Object::connect(m_Content, &Content::Updated, this, &vtkCylinder::contentUpdate);
 }
 
 vtkCylinder::~vtkCylinder() {
-  m_Actor->Delete();
+  if (m_Actor) m_Actor->Delete();
+  if (m_VtkAsm) m_VtkAsm->Delete();
 }
 
 void vtkCylinder::contentUpdate() {
@@ -53,28 +55,31 @@ void vtkCylinder::contentUpdate() {
   vtkProp3D* root = vtkProp3D::SafeDownCast(this->GetProp());
   if (!root) return;
 
+  // 1. Placement (Position/Rotation/Model-level Scale) goes to the root prop
   vtkMatrix4x4* vmat = root->GetUserMatrix();
   if (!vmat) {
     vtkNew<vtkMatrix4x4> mat;
     root->SetUserMatrix(mat);
     vmat = mat;
   }
-
-  // Multiply the placement matrix by the volume scaling (Radius, Radius, Height)
-  Matrix4f transform = m_Content->GetMatrix() * m_Content->GetLocalMatrix();
+  Matrix4f transform = m_Content->GetMatrix();
   Matrix4fToVtk(transform, vmat);
 
-  // Update internal alignment based on active axis
+  // 2. Shape-local properties (Radius, Height, Axis alignment) go to the internal actor
   vtkTransform* alignment = vtkTransform::SafeDownCast(m_Actor->GetUserTransform());
   if (alignment) {
       alignment->Identity();
+      alignment->PostMultiply();
+      
+      // Initial source is centered Y-cylinder (Radial XZ [-1,1], Height Y [-0.5, 0.5])
+      // Apply Radius and Height scaling
+      alignment->Scale(m_Content->GetRadius(), m_Content->GetHeight(), m_Content->GetRadius());
+
+      // Apply Axis alignment
       int axis = m_Content->GetAxis();
       if (axis == 0) alignment->RotateZ(-90); // Y -> X
       else if (axis == 1) ;                   // Y -> Y (identity)
       else if (axis == 2) alignment->RotateX(90);  // Y -> Z
-      
-      // We keep it centered as per latest user preference in Step 677
-      // alignment->Translate(0, 0, 0); // Implicit
   }
 
   root->Modified();
@@ -90,16 +95,9 @@ void vtkCylinder::Update() {
   vtkMatrix4x4* vmat = root->GetUserMatrix();
   if (!vmat) return;
   
-  Matrix4f fullTransform = VtkToMatrix4f(vmat);
-  Matrix4f placementScale = m_Content->GetLocalMatrix().inverse();
-  Matrix4f transform = fullTransform * placementScale;
-
-  if (m_Content->GetParent()) {
-    Matrix4f localT = m_Content->GetParent()->GetWorldMatrix().inverse() * transform;
-    m_Content->SetMatrix(localT);
-  } else {
-    m_Content->SetMatrix(transform);
-  }
+  // Pull the placement matrix directly from VTK
+  Matrix4f transform = VtkToMatrix4f(vmat);
+  m_Content->SetMatrix(transform);
 
   m_Content->Updated();
 }
@@ -108,36 +106,27 @@ void vtkCylinder::InstallPipe() {
   if (!m_Content)
     return;
 
+  m_VtkAsm = ::vtkAssembly::New();
+  this->SetProp(m_VtkAsm);
+
   vtkNew<vtkCylinderSource> cylinder;
   cylinder->SetRadius(1.0);
   cylinder->SetHeight(1.0);
   cylinder->SetResolution(32);
 
+  m_Actor = vtkActor::New();
   vtkNew<vtkTransform> alignment;
-  alignment->Identity();
-  alignment->Translate(0, 0, -0.5);
-
-  // Default to Y alignment (Identity) as per latest request
-  int axis = m_Content->GetAxis();
-  if (axis == 0) alignment->RotateZ(-90);
-  else if (axis == 2) alignment->RotateX(90);
+  m_Actor->SetUserTransform(alignment);
 
   vtkNew<vtkPolyDataMapper> mapper;
   mapper->SetInputConnection(cylinder->GetOutputPort());
-  
   m_Actor->SetMapper(mapper);
-  m_Actor->SetUserTransform(alignment);
   m_Actor->GetProperty()->SetRepresentationToWireframe();
   m_Actor->GetProperty()->SetAmbient(0.6);
 
-  this->SetProp(m_Actor);
-  
-  vtkProp3D* root = vtkProp3D::SafeDownCast(this->GetProp());
-  if (root) {
-      vtkNew<vtkMatrix4x4> vmat;
-      Matrix4fToVtk(m_Content->GetMatrix() * m_Content->GetLocalMatrix(), vmat);
-      root->SetUserMatrix(vmat);
-  }
+  m_VtkAsm->AddPart(m_Actor);
+
+  this->contentUpdate();
 }
 
 } // namespace Vtk
diff --git a/src/Vtk/Math/vtkCylinder.h b/src/Vtk/Math/vtkCylinder.h
index 20ce7a5..fc246f9 100644
--- a/src/Vtk/Math/vtkCylinder.h
+++ b/src/Vtk/Math/vtkCylinder.h
@@ -29,6 +29,7 @@
 #include "Math/Cylinder.h"
 #include "Vtk/uLibVtkInterface.h"
 #include <vtkActor.h>
+class vtkAssembly;
 
 namespace uLib {
 namespace Vtk {
@@ -53,11 +54,14 @@ public:
   /** Synchronizes the uLib model matrix with the VTK actor (e.g., after UI manipulation) */
   virtual void Update();
 
+  virtual uLib::Object* GetContent() const override { return (uLib::Object*)m_Content; }
+
 protected:
   /** Sets up the VTK visualization pipeline */
   virtual void InstallPipe();
 
   vtkActor *m_Actor;
+  ::vtkAssembly *m_VtkAsm;
   Content *m_Content;
 };
 
diff --git a/src/Vtk/uLibVtkInterface.h b/src/Vtk/uLibVtkInterface.h
index 66cff0e..7110f2f 100644
--- a/src/Vtk/uLibVtkInterface.h
+++ b/src/Vtk/uLibVtkInterface.h
@@ -61,6 +61,8 @@ public:
 
   virtual vtkPropCollection *GetProps();
 
+  virtual uLib::Object *GetContent() const { return nullptr; }
+
   void ConnectRenderer(vtkRenderer *renderer);
 
   void DisconnectRenderer(vtkRenderer *renderer);
diff --git a/src/Vtk/vtkObjectsContext.cpp b/src/Vtk/vtkObjectsContext.cpp
index 133f926..6f157c5 100644
--- a/src/Vtk/vtkObjectsContext.cpp
+++ b/src/Vtk/vtkObjectsContext.cpp
@@ -1,6 +1,7 @@
 #include "vtkObjectsContext.h"
 #include "Vtk/Math/vtkContainerBox.h"
 #include "Vtk/Math/vtkCylinder.h"
+#include "Vtk/Math/vtkAssembly.h"
 #include "HEP/Detectors/vtkDetectorChamber.h"
 
 #include <vtkAssembly.h>
@@ -42,12 +43,8 @@ void vtkObjectsContext::Synchronize() {
       it->second->DisconnectRenderer(nullptr); // If we have a ref to a renderer we should disconnect but Puppet doesn't store it easily
       // Actually Puppet::DisconnectRenderer(vtkRenderer*) needs the renderer.
       // For now we just remove from assembly
-      vtkPropCollection* props = it->second->GetProps();
-      props->InitTraversal();
-      while(vtkProp* prop = props->GetNextProp()) {
-          if (vtkProp3D* p3d = vtkProp3D::SafeDownCast(prop))
-            m_Assembly->RemovePart(p3d);
-      }
+      if (auto* p3d = vtkProp3D::SafeDownCast(it->second->GetProp()))
+          m_Assembly->RemovePart(p3d);
       this->PuppetRemoved(it->second);
       delete it->second;
       it = m_Puppets.erase(it);
@@ -62,12 +59,8 @@ void vtkObjectsContext::Synchronize() {
       Puppet* puppet = this->CreatePuppet(obj);
       if (puppet) {
         m_Puppets[obj] = puppet;
-        vtkPropCollection* props = puppet->GetProps();
-        props->InitTraversal();
-        while(vtkProp* prop = props->GetNextProp()) {
-            if (vtkProp3D* p3d = vtkProp3D::SafeDownCast(prop))
-                m_Assembly->AddPart(p3d);
-        }
+        if (auto* p3d = vtkProp3D::SafeDownCast(puppet->GetProp()))
+            m_Assembly->AddPart(p3d);
         this->PuppetAdded(puppet);
       }
     }
@@ -80,12 +73,8 @@ void vtkObjectsContext::OnObjectAdded(uLib::Object* obj) {
     Puppet* puppet = this->CreatePuppet(obj);
     if (puppet) {
       m_Puppets[obj] = puppet;
-      vtkPropCollection* props = puppet->GetProps();
-      props->InitTraversal();
-      while(vtkProp* prop = props->GetNextProp()) {
-          if (vtkProp3D* p3d = vtkProp3D::SafeDownCast(prop))
-              m_Assembly->AddPart(p3d);
-      }
+      if (auto* p3d = vtkProp3D::SafeDownCast(puppet->GetProp()))
+          m_Assembly->AddPart(p3d);
       this->PuppetAdded(puppet);
     }
   }
@@ -97,12 +86,8 @@ void vtkObjectsContext::OnObjectRemoved(uLib::Object* obj) {
     if (it != m_Puppets.end()) {
         // For now we just remove from assembly. 
         // Puppet::DisconnectRenderer(vtkRenderer*) needs the renderer, but we don't have it here easily.
-        vtkPropCollection* props = it->second->GetProps();
-        props->InitTraversal();
-        while(vtkProp* prop = props->GetNextProp()) {
-            if (vtkProp3D* p3d = vtkProp3D::SafeDownCast(prop))
-                m_Assembly->RemovePart(p3d);
-        }
+        if (auto* p3d = vtkProp3D::SafeDownCast(it->second->GetProp()))
+            m_Assembly->RemovePart(p3d);
         this->PuppetRemoved(it->second);
         delete it->second;
         m_Puppets.erase(it);
@@ -131,6 +116,8 @@ Puppet* vtkObjectsContext::CreatePuppet(uLib::Object* obj) {
     return new vtkDetectorChamber(static_cast<uLib::DetectorChamber*>(obj));
   } else if (std::strcmp(className, "Cylinder") == 0) {
     return new vtkCylinder(static_cast<uLib::Cylinder*>(obj));
+  } else if (std::strcmp(className, "Assembly") == 0) {
+    return new Assembly(static_cast<uLib::Assembly*>(obj));
   }
   
   // Fallback if we don't know the exact class but it might be a context itself
diff --git a/src/Vtk/vtkObjectsContext.h b/src/Vtk/vtkObjectsContext.h
index 0408e47..cfb480a 100644
--- a/src/Vtk/vtkObjectsContext.h
+++ b/src/Vtk/vtkObjectsContext.h
@@ -25,6 +25,8 @@ public:
   /** @brief Returns the puppet associated with a specific core object. */
   Puppet* GetPuppet(uLib::Object* obj);
 
+  const std::map<uLib::Object*, Puppet*>& GetPuppets() const { return m_Puppets; }
+
   /** @brief Updates all managed puppets. */
   virtual void Update() override;
 
diff --git a/src/Vtk/vtkViewport.cpp b/src/Vtk/vtkViewport.cpp
index 58bed5d..d05522b 100644
--- a/src/Vtk/vtkViewport.cpp
+++ b/src/Vtk/vtkViewport.cpp
@@ -6,6 +6,7 @@
 #include <vtkProp3DCollection.h>
 #include <vtkCamera.h>
 #include <algorithm>
+#include <functional>
 #include <vtkInteractorStyleTrackballCamera.h>
 #include <vtkObjectFactory.h>
 #include <vtkAxesActor.h>
@@ -29,6 +30,12 @@
 #include <iostream>
 #include <cstdlib>
 #include "vtkHandlerWidget.h"
+#include "vtkObjectsContext.h"
+#include "Math/Assembly.h"
+#include "Math/ContainerBox.h"
+#include "Math/Cylinder.h"
+#include "Math/Transform.h"
+#include "Vtk/Math/vtkAssembly.h"
 
 namespace uLib {
 namespace Vtk {
@@ -220,32 +227,67 @@ void Viewport::SetupPipeline(vtkRenderWindowInteractor* iren)
         self->pv->m_Picker->Pick(pos[0], pos[1], 0, self->pv->m_Renderer);
         vtkProp* picked = self->pv->m_Picker->GetViewProp();
         
+        // 1. Recursive helper to check if a container prop contains a target prop
+        std::function<bool(vtkProp*, vtkProp*)> containsProp;
+        containsProp = [&containsProp](vtkProp* container, vtkProp* target) -> bool {
+            if (container == target) return true;
+            vtkPropCollection* parts = nullptr;
+            if (auto* pa = vtkPropAssembly::SafeDownCast(container))
+                parts = pa->GetParts();
+            else if (auto* aa = vtkAssembly::SafeDownCast(container))
+                parts = aa->GetParts();
+            if (parts) {
+                parts->InitTraversal();
+                for (int i = 0; i < parts->GetNumberOfItems(); ++i) {
+                    if (containsProp(parts->GetNextProp(), target))
+                        return true;
+                }
+            }
+            return false;
+        };
+
         Puppet* target = nullptr;
         if (picked) {
+            // 2. Find the leaf puppet: the one that contains 'picked' and is not a parent of another that also contains it.
+            // Actually, we can just find all matches and pick the one with most 'nested' prop?
+            // A simpler way: we know 'picked' is the LEAF prop from VTK.
+            // Find a puppet that contains it.
+            Puppet* leafPuppet = nullptr;
             for (auto* p : self->m_Puppets) {
-                if (p->GetProp() == picked) {
-                    target = p;
-                    break;
+                if (containsProp(p->GetProp(), picked)) {
+                    // If we already have a candidate, check if this one is smaller (nested)
+                    if (!leafPuppet || containsProp(leafPuppet->GetProp(), p->GetProp())) {
+                        leafPuppet = p;
+                    }
                 }
-                auto* propAssembly = vtkPropAssembly::SafeDownCast(p->GetProp());
-                auto* actorAssembly = vtkAssembly::SafeDownCast(p->GetProp());
-                vtkPropCollection* parts = nullptr;
-                if (propAssembly) parts = propAssembly->GetParts();
-                else if (actorAssembly) parts = actorAssembly->GetParts();
+            }
 
-                if (parts) {
-                    bool found = false;
-                    parts->InitTraversal();
-                    for (int i=0; i<parts->GetNumberOfItems(); ++i) {
-                        if (parts->GetNextProp() == picked) {
-                            found = true;
-                            break;
+            if (leafPuppet) {
+                target = leafPuppet;
+                
+                // 3. Model-driven hierarchy climb:
+                // If the leaf puppet has a uLib object, climb its parents.
+                // If any parent is an Assembly with GroupSelection=true, select the assembly puppet instead.
+                uLib::Object* currentObj = leafPuppet->GetContent();
+
+                while (currentObj) {
+                    // Object doesn't have parent, but AffineTransform does
+                    uLib::Object* parentObj = nullptr;
+                    if (auto* at = dynamic_cast<uLib::AffineTransform*>(currentObj)) {
+                        parentObj = dynamic_cast<uLib::Object*>(at->GetParent());
+                    }
+
+                    if (auto* parentAsm = dynamic_cast<::uLib::Assembly*>(parentObj)) {
+                        if (parentAsm->GetGroupSelection()) {
+                            // Find the puppet for this parent assembly
+                            auto it = self->m_ObjectToPuppet.find(parentAsm);
+                            if (it != self->m_ObjectToPuppet.end()) {
+                                target = it->second;
+                                // Keep climbing to find even larger groups
+                            }
                         }
                     }
-                    if (found) {
-                        target = p;
-                        break;
-                    }
+                    currentObj = parentObj;
                 }
             }
         }
@@ -387,20 +429,74 @@ void Viewport::ZoomSelected()
 
 void Viewport::AddPuppet(Puppet& prop)
 {
-    m_Puppets.push_back(&prop);
-    prop.ConnectRenderer(pv->m_Renderer);
+    this->RegisterPuppet(&prop, false);
     Render();
 }
 
 void Viewport::RemovePuppet(Puppet& prop)
 {
-    if (prop.IsSelected()) SelectPuppet(nullptr);
-    auto it = std::find(m_Puppets.begin(), m_Puppets.end(), &prop);
-    if (it != m_Puppets.end()) m_Puppets.erase(it);
-    prop.DisconnectRenderer(pv->m_Renderer);
+    this->UnregisterPuppet(&prop);
     Render();
 }
 
+void Viewport::RegisterPuppet(Puppet* p, bool isPart) {
+    if (!p) return;
+    if (std::find(m_Puppets.begin(), m_Puppets.end(), p) != m_Puppets.end()) return;
+    
+    m_Puppets.push_back(p);
+    p->ConnectRenderer(pv->m_Renderer);
+
+    // If it's a part of an assembly, we don't want to draw it twice.
+    // Assembly itself already draws its parts. 
+    // But we need ConnectRenderer above to allow highliting and property updates.
+    if (isPart) {
+        pv->m_Renderer->RemoveViewProp(p->GetProp());
+    }
+
+    // Get the object and register in map
+    uLib::Object* obj = p->GetContent();
+    
+    // If it's an assembly, we need to observe its children
+    if (auto* as = dynamic_cast<::uLib::Vtk::Assembly*>(p)) {
+        this->ObserveContext(as->GetChildrenContext());
+    }
+    
+    if (obj) m_ObjectToPuppet[obj] = p;
+}
+
+void Viewport::UnregisterPuppet(Puppet* p) {
+    if (!p) return;
+    if (p->IsSelected()) SelectPuppet(nullptr);
+    
+    auto it = std::find(m_Puppets.begin(), m_Puppets.end(), p);
+    if (it != m_Puppets.end()) m_Puppets.erase(it);
+
+    // Remove from map
+    for (auto mapIt = m_ObjectToPuppet.begin(); mapIt != m_ObjectToPuppet.end(); ) {
+        if (mapIt->second == p) mapIt = m_ObjectToPuppet.erase(mapIt);
+        else ++mapIt;
+    }
+    
+    p->DisconnectRenderer(pv->m_Renderer);
+}
+
+void Viewport::ObserveContext(vtkObjectsContext* ctx) {
+    if (!ctx) return;
+    
+    // Process existing puppets
+    for (auto const& [obj, puppet] : ctx->GetPuppets()) {
+        this->RegisterPuppet(puppet, true);
+    }
+    
+    // Listen for future puppets
+    uLib::Object::connect(ctx, &vtkObjectsContext::PuppetAdded, [this](Puppet* p){
+        this->RegisterPuppet(p, true);
+    });
+    uLib::Object::connect(ctx, &vtkObjectsContext::PuppetRemoved, [this](Puppet* p){
+        this->UnregisterPuppet(p);
+    });
+}
+
 void Viewport::SelectPuppet(Puppet* prop)
 {
     for (auto* p : m_Puppets) {
diff --git a/src/Vtk/vtkViewport.h b/src/Vtk/vtkViewport.h
index 09266e1..173ce3f 100644
--- a/src/Vtk/vtkViewport.h
+++ b/src/Vtk/vtkViewport.h
@@ -3,6 +3,9 @@
 
 #include "uLibVtkInterface.h"
 #include <vector>
+#include <map>
+
+namespace uLib { class Object; }
 
 // VTK classes are in the global namespace
 class vtkRenderer;
@@ -73,10 +76,16 @@ protected:
     void SetupPipeline(vtkRenderWindowInteractor* iren);
 
     void UpdateGrid();
+    
+    // Internal puppet registration
+    void RegisterPuppet(Puppet* p, bool isPart = false);
+    void UnregisterPuppet(Puppet* p);
+    void ObserveContext(class vtkObjectsContext* ctx);
 
     struct ViewportData *pv;
     Axis                                         m_GridAxis;
     std::vector<Puppet*>                         m_Puppets;
+    std::map<uLib::Object*, Puppet*>             m_ObjectToPuppet;
 };
 
 } // namespace Vtk