This isn’t something new, but a feature that was on my to do list for years after seeing it implemented elsewhere.
The idea is simple. You take a 2D CA and rather than render each step/cycle/update as a 2D image, you add the current 2D cell states as a layer of a 3D stack of cubes. Each slice of the cube is another step in the CA generation.
These examples are of History Dependent Cellular Automata.
Once again I must give a shout out to the most excellent Mitsuba Renderer. I would not be able to render these examples with such nicely shaded cubes without it.