A Greek philosopher Democritus first gave the idea of the atom in 450 B.C.He considered a piece of matter and starts dividing it into smaller and much smaller pieces and in the end, there was a point when the matter cannot be divided into more fine particles.
He called these individual unit atomos which were later termed Atoms.
John Dalton revives the idea of Democritus and starts working on this and doing many experimental works to prove the existence of atoms.
Thus, John Dalton known as father of atoms and atomic theory.