The gyroid is a minimal surface that chops space into two parts. This is a portion of it, made into an elegant sculpture by Bathsheba Grossman.
A minimal surface is a surface in ordinary 3d space that can’t reduce its area by changing shape slightly. You can create a minimal surface by building a wire frame and then creating a soap film on it. As long as the soap film doesn’t actually enclose any air, it will try to minimize its area – so it will end up being a minimal surface.