jan 1, 1886 - Eugen Goldstein discovered the proton.
He observed a cathode ray, which is a stream of electrons produced at the negative electrode of a tube that has a low pressure gas inside, and saw some rays traveling in the opposite direction of the actual cathode ray made by the electrons. He concluded that those were protons, the positively charged subatomic particle. His discovery proved that the atom was made up of smaller particles and was a huge part of creating different atomic models to show what and how the atom was composed of and that there were, in fact, smaller things than the atom itself.
Added to timeline:
The Atom vs the Telephone