Six octahedra are placed at the vertices of a larger octahedron. The voids within the large octahedron are filled with tetrahedra to form a composite solid octahedron, which is then placed at the vertices of yet another octahedron, and the voids again are filled with tetrahedra. This process constitutes two stages of a fractal structure. Separate the parts in stage 1 or stage 2 to see how the fractal is assembled.