3 - Platonic solids
There are only five solids with each edge the same length, each angle equal, and each corner alike:
Tetrahedron
Octahedron
Icosahedron
Hexahedron
or Cube
Dodecahedron
These are called
regular polyhedra
, or
Platonic solids
.
These pictures are from the Wikipedia article on
Platonic solids
. Permission to use them was granted under the
GNU Free Documentation License
.