Hyperdodecahedron in a Bathroom

Tip: the full-screen button is usually on the bottom right of the video.

If you're confused, this video of an MRI provides an analogy:

An MRI is a series of 2D slices that reveals a 3D shape.
The video above is a series of 3D slices that reveals a four-dimensional shape.

More details at the Github repository to generate this video (scroll down to see the README).