5: The Atom Is the Smallest Particle in Existence

Believe it or not, we weren't actually all that stupid in ancient times. The idea that matter was composed of smaller, individual units (atoms) has been around for thousands of years -- but the idea that there was something smaller than that was a bit harder to come by.

It wasn't until the early 20th century, when physicists like J.J. Thompson, Ernest Rutherford, James Chadwick and Neils Bohr came along, that we started to sort out the basics of particle physics: protons, neutrons and electrons and how they make an atom what it is. Since then, we've come a long way: on to charmed quarks and Higgs bosons, anti-electrons and muon neutrinos. Let's hope it doesn't get too much more complicated than that.