Quarks are the fundamental particles that make up protons and neutrons, as well as several other types of particles. There are six types of quarks, which are referred to as different “flavors.” These are named up, down, top, bottom, charm, and strange. Protons and neutrons are each made up of three quarks. Two up and one down quark make up a proton. Two down and one up quark make up a neutron.