The gyroid is a "triply periodic minimal surface" that dives all space into two congruent regions. A minimal surface is a surface for which every piece of the surface has the smallest possible area needed to span the boundary of that piece. You can find minimal surfaces in real life by dipping a wire frame into soapy water.
This beautiful steel/bronze representation of the gyroid was created by Bathsheba Grossman. 1.4"L x 1.4"W x 1.4"H