There are possibly three or four types of quark. It is even possible that quarks themselves may be made up of still more fundamental particles. A particle that is acted upon by the strong force. The neutron, for example, is built of three quarks. Five types of quarks have been discovered, and it is believed that a sixth also exists.
Quarks interact mainly via the strong nuclear force and the electromagnetic force.
The hypothetical constituent of the elementary particles that interacts via glue forces. For a variety of theoretical reasons, free quarks can never be seen. According to the theory of quantum chromodynamics, protons, neutrons, and their higher-energy cousins are composed of trios of quarks, while the mesons are each made of one quark and one antiquark. A phase transition in the early universe when freely roaming quarks combined to form neutrons, protons, and other strongly interacting particles called hadrons. The brightest objects in the universe, quasars can generate over a trillion times as much light as the Sun from a region little larger than the solar system.