Diagrams are essential for communicating the structure of complex 3D objects such as mechanical assemblies, architectural environments and biological organisms. Yet, creating illustrations that clearly depict the structural relationships between the parts of such objects is not an easy task. The primary problem is occlusion -- important interior structures are often hidden by opaque exterior surfaces. Therefore, illustrators use conventions such as exploded views, cutaways, ghosting (i.e. varying the transparency of the occluder), and hidden-object stylization (i.e. varying the rendering style of the hidden object) to reduce or eliminate occlusions and reveal internal parts. In this talk I'll present several interactive systems that are based on these design conventions and make it easy to generate illustrative diagrams of complex 3D objects.