Democritus was a pre-Socratic Greek philosopher from Abdera, primarily remembered today for his formulation of an atomic theory of the universe. Democritus wrote extensively on a wide variety of topics. c. 460 BC – c. 360 BC; died at about 100. Alive at the same time as Sophocles, Hippocrates, Thucydides, Apelles, and Aristotle. Wiki link