The Smallest Things Scientists and even non-scientists know things today that the great physicists of a century ago couldn't have imagined. For example, physicists in those days believed that the smallest things in the universe, the foundation of all matter, were atoms, a word derived from a Greek word meaning"uncuttable." Nowadays, however, we are simply not sure what the smallest particle in the universe Atoms are made of particles called protons neutrons, and electrons, Protons and neutrons(the"hadrons" that give the collider its name) are made of even smaller particles named quarks and gluons, which have been detected in collider experiments; experimental proof for the existence of quarks came in 1968 and for gluons in 1979.