Particle accelerators are the primary experimental tool used in particle physics experiments. They accelerate beams of charged particles—such as protons, electrons, and ions—to very high speeds. In a particle physics experiment, the fast-moving beams are steered into a collision either with a stationary target or a beam traveling in the opposite direction. These collisions release a tremendous amount of energy that can create new particles. Much of the Standard Model was developed by studying the particles produced in such collisions. See: cyclotron, linac, synchrotron.