(c. 460 - c. 370 BCE)
Demokritos of Abdura (Ancient Thrace) was a Presocratic
Nature Philosopher who posed the Atomic Hypothesis: everything that exits is composed of invisibly small and indivisible (atomon)
particles that have always and will always exist.
Read more about Demokritos.
Read a more detailed account of Demokritos from the Stanford Encyclopedia of Philosophy