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 # Parts and components

 Last update: 09.03.2026 

A Part contains zero or more DesignBody objects and zero or more Component objects. This means a part can contain both design bodies and components, in which case it's neither a pure piece part, nor a pure assembly. This is supported so that the interactive user can restructure design bodies into components, or vice versa.

A component is an *instance* of a *template* part. It has a *placement* matrix to position the component into assembly space. The template is neither a child nor a parent of the component. If the parent-child hierarchy is visualized as an inverted tree structure with the root at the top and leaf nodes at the bottom, then the template is a sideways reference to another part, which is the root of another hierarchy.![](/sites/default/files/git_ansys/discovery_extensibility_guide_2026_r1_2/clip_image002_-854738110.png)

The template part may live in the same document as the component, giving rise to what the interactive user would call an *internal component*, or it may live in another document, giving rise to an *external component*. Strictly speaking, it's the template part that's either internal or external, not the component itself.