Anaxagoras
500 BC - 428 BC
Greek philosopher Anaxagoras held that infinitesimal parts male up objects, and each part contains a mixture of every different type of matter.
https://en.wikipedia.org/wiki/Anaxagoras
“The Greeks do not think correctly about coming-to-be and passing-away; for no thing comes to be or passes away, but is mixed together and dissociated from the things that are. And thus they would be correct to call coming-to-be mixing-together and passing-away dissociating”
Anaxagoras