Quarks Quarks- any group of subatomic particles believed to be among the basic Quarks are believed to be the fundamental constituents of matter, and have no apparent structure. They are the particles that make up protons and neutrons, which make up the nucleus of atoms. Also, particles that interact by means of the strong force, the force that holds parts of the nucleus together, are explained in terms of quarks. Other baryons are explained in terms of quarks(1985 Quarks). Quarks have mass and exhibit spin, the type of intrinsic angular momentum corresponding to rotation around an axis, equal to half the basic quantum mechanical unit of angular momentum, obeying Pauli's exclusion