Historical Introduction to Particle Physics

There are leptons (lightweight particles), the electron, muon, tau particle, and their antiparticles, like positron for electron. With their antiparticles, they also have their neutrino partners. Then, of course, there are protons and neutrons, which are hadrons. These are middleweight mesons, like pions and kaons, and heavyweight baryons, like protons and neutrons. They are made of quarks. Mesons are made of a quark-antiquark pair and baryons three quarks.