For example, let's say you have a big sweep that represents a large part of a Building, and that Sweep is inside an in-place Generic Model family in the project.
Firstly, use some Voids to cut the sweep into the sections or pieces that you want...
Then, if you edit the underlying Family and divide it with more Voids, Revit will automatically create and update the Part elements as needed. Very cool.
From here, you can export those Parts to Navisworks for animation or sequencing, if you so desire.