In geometry, the rhombic dodecahedron is a convex polyhedron with 12 congruent rhombic faces. It has 24 edges, and 14 vertices of 2 types. It is a Catalan solid, and the dual polyhedron of the cuboctahedron.
Rhombic Dodecahedral Honeycomb
The rhombic dodecahedral honeycomb (also dodecahedrille) is a spacefilling tessellation (or honeycomb) in Euclidean 3space. It is the Voronoi diagram of the facecentered cubic spherepacking, which has the densest possible packing of equal spheres in ordinary space (see Kepler conjecture).
In Dungeons and Dragons
”I’ve never seen a rhombic dodecahedron d12 before. They do exist after a quick search, but the much more common d12 is just a dodecahedron, with pentagonal faces.”
The UCLA^{1} investigators developed a technique that prevents that corrosion and showed that, in its absence, lithium atoms assemble into a surprising shape—the rhombic dodecahedron, a 12sided figure similar to the dice used in roleplaying games like Dungeons and Dragons.
Footnotes

University of California, Los Angeles ↩