The tetrakaidecahedron embeded in a BCC unit cell

The 14-sided tetrakaidecahedron, obtainable by truncating an octahedron, can monohedrally fill space and has been considered as the shape of a model grain, with respect to minimal surface area. It is the polyhedron obtained by a Voronoi tessellation/division of a BCC lattice and is also the shape of the first Brillouin zone for the FCC lattice.