A quark (or )'s an elementary particle and a fundamental constituent of matter. Quarks combine to form composite particles called hadrons, the best-known of which are protons and neutrons. They're the only particles in the Standard Model to experience all four fundamental interactions, also known as fundamental forces. Due to a phenomenon known as color confinement, quarks are never found in isolation; they can only be found within hadrons. For this reason, much of what's known about quarks has… (More on Quark)