Materialism is a form of philosophical monism that holds that matter is the fundamental substance of nature and that all phenomena are identical with material interactions. It belongs to the class of monist ontology and developed in several regions of Eurasia during the Axial Age from approximately 800-200 BC. Materialism asserts that all that exists is matter and void, and that all phenomena result from different motions and conglomerations of basic material particles called atoms.