(c.460-370 BC)Later known as the Laughing Philosopher, Democritus as born i Thrace, and is best known for developing his teacher Leucippos' atomic theory of the universe.

Democritus stated that all matter consists of tiny, indestructible units called atoma (indivisibles) which infinitely moves around in the void. These theories were known widely through Epicerus.

Democritus got his nickname because he believed happiness is the greatest good and can be achieved when someone practices moderation, calm and freedom from fear.