Charlotte Woodward took this picture. The preschooler was 4 years, 3 months when it was taken, and he wanted to use THESE structures, these were his favorites.
If you are familiar with the Platonic Solids, they closely resemble icosahedra, but they are really 20 Sierpinski Tetrahedra packed together. There are gaps between the tetrahedra, hard to recognize in these small sizes/iterations, especially from far away. I stumbled onto this structure when planning for a trip to Germany as a way to carry my tetrahedron families safely in the baggage compartment of the plane. Each has on the interior the entire previous structure with an added outside section, but it is NOT a fractal structure,because the pieces, as you can see, are tetrahedra, and the outside shape of the structure is icosahedron-like. I call it an STIcosa, for a "Sierpinski Tetrahedron Icosahedron" or better put, (what appears to be) an Icosahedron made up of 20 Sierpinski Tetrahedra.