Take the quarks as an example. In addition to the pair of quark types known as "up" and "down," which make up the core of atomic nuclei, there exist two additional quark pairs: "charm" and ...

Protons and neutrons are not, each being made of three quarks. Protons have two up quarks and one down quark, and neutrons are made of one up and two downs. However, four other types of quarks exist.