I find it interesting that 2,500 years ago, there was evidence that atoms existed. The Greek philosopher Leucippus first developed the idea, and is the originator of ancient Atomist philosophy. According to a Stanford University Web site:
These ancient atomists theorized that the two fundamental and oppositely characterized constituents of the natural world are indivisible bodies—atoms—and void. The latter is described simply as nothing, or the negation of body. Atoms are by their nature intrinsically unchangeable; they can only move about in the void and combine into different clusters. Since the atoms are separated by void, they cannot fuse, but must rather bounce off one another when they collide. Because all macroscopic objects are in fact combinations of atoms, everything in the macroscopic world is subject to change, as their constituent atoms shift or move away. Thus, while the atoms themselves persist through all time, everything in the world of our experience is transitory and subject to dissolution.
plato.stanford.edu/entries/atomism-ancient/Leucippus, like Einstein, was a genius at using simple ideas to express profound truths. Leucippus made this argument for the existence of atoms:
Lets say you and i were at a certain distance from one another, and we began to walk toward one another. We would never meet. Why? Because as we approached each other, we would cut the distance in half. As we continued to walk toward one another, the distance will be halved again. This would continue until we clasped hands, and yet we would still not meet, for the distance between us, although divided, would never be zero. This is certainly the case, for if you and i shake hands, NE, the atoms in my hand will never touch those in your hand. In fact, the atoms in your own hand never touch each other.