Protons and neutrons are made up of quarks. Quarks are subatomic particles, but they are also elementary particles because we do not know if they are made up of even smaller particles. There are six different types of quarks. These are the up quark, the down quark, the strange quark, the charm quark, the bottom quark, and the top quark. A neutron is made of two down quarks and one up quark. The proton is made up of two up quarks and one down quark.