Earlier Concepts:

Plato figured out that particles had regular mathematical shape. The polyhedra are, generally, called regular platonic solids. For e.g., earth was a cube, air was an octahedron etc. The flat faces of each of these shapes can be made from two kinds of triangle. According to Plato, these triangles are the fundamental particles of nature. They pervade all space. The elements are converted by rearranging the triangles into new geometric form.