The ElementsTimaeus claims that the minute particle of each element had a special geometric shape: tetrahedron (fire), octahedron (air), icosahedron (water), and cube (earth).
Tetrahedron (fire) Octahedron (air) Icosahedron (water) Cube (earth)
The Timaeus makes conjectures on the composition of the four elements which some ancient Greeks thought constituted the physical universe: earth, water, air, and fire. Timaeus links each of these elements to a certain Platonic solid: the element of earth would be a cube, of air an octahedron, of water an icosahedron, and of fire a tetrahedron. Each of these perfect polyhedra would be in turn composed of trianagular faces the 30-60-90 and the 45-45-90 triangles. The faces of each element could be broken down into its component right-angled triangles, either isosceles or scalene, which could then be put together to form all of physical matter. Particular characteristics of matter, such as water's capacity to extinguish fire, was then related to shape and size of the constituent triangles. The fifth element (i.e. Platonic solid) was the dodecahedron, whose faces are not triangular, and which was taken to represent the shape of the Universe as a whole, possibly because of all the elements it most approximates a sphere, which Timaeus has already noted was the shape into which God had formed the Universe..
The extensive final part of the dialogue addresses the creation of humans, including the soul, anatomy, perception, and transmigration of the soul.