Platonic Solids are the shapes which form parts of Sacred Geometry.
They were first cataloged by the ancient philosopher, Plato
Also DaVinci interested in and contributed with his outlines
The last four shapes correspond with the elements: water (Icosahedron), air (octahedron), fire (tetrahedron), and earth (hexahedron) : with the first-base : dodecahedron, representing heaven, ether or the Universe.
The shapes that form the five original Platonic Solids occur naturally in nature, and indeed in the crystal world.