OG philosopher, genious businessman, and an overall smart guy.
There's a story where he earned a lot of money by predicting how olive market will behave, which he had figured out because of the climate that year. He basically lived in a world where everything was believed an act of god, and his understanding of the fact that's not true led him to a better understanding of the world around him. He "got rich just to prove how easy it is".
Famous for idea that "everything is made of water".
Founder of Milesian school of Philosophy. His most notable student was Anaximander ("first people survived infancy because they developed in the belly of a fish" guy)