They are formed by elementary particles called electrons, protons, and neutrons. In Ancient Greece, Leucippus and Democritus had been searching for an explanation for the Universe's origin. Their theory suggested that the principle of everything was something indivisible and indestructible — in greek, atom means “something that cannot be divided”. However, the 'father of modern atomism' is the British physicist John Dalton. He based his work on the ideas of Leucippus and Democritus, creating “Dalton’s Atomic Model”, in which he proposed that all atoms are massive and indestructible. For example, if an atom was the size of a football stadium, its core would be the size of a pea, but it would be so dense that would contain roughly all of their mass.
