Particle Physics: the study of the elementary building blocks of matter and radiation and their interaction. The fundamental particles are summarised by the standard model. This includes leptons, the quarks that make up protons and neutrons, and gauge bosons, which mediate forces between the other particles. Modern particle physics research is focused on subatomic particles, including atomic constituents such as electrons, protons, and neutrons, produced by radioactive and scattering processes, such as photons, neutrinos, and muons, as well as a wide range of exotic particles.