This famous pre-Socratic philospher (460-370BC) was a prolific writer on a wide variety of topics. Sadly none of his works survives, so we know of him only through second-hand references, most of which are by Aristotle, who regarded him as a bit of a rival in the world of natural philosphy.
In ancient Greek 'atomos' means 'not cuttable/splittable', something that could not be further divided. In Demokritos' philosophy, and that of his teacher Leucippus, these 'atomoi' (indivisible entities) moved through empty space - the 'void' - and combined in different ways to form everything in the universe. Today of course, atoms can be split into sub-atomic particles, but the name remains as a tribute to Demokritos' prescient idea.
Demokritos was a passionate observer of the natural world, believing that reason and curiosity were the keys to our understanding of reality. Known as 'The Laughing Philosopher', he greeted life's absurdities with humour, maintaining that happiness comes from wisdom, moderation, and a mind at peace.
He travelled extensively - by all accounts getting all the way to India and Egypt! - and had an insatiable thirst for learning new things.