An elementary particle is a subatomic particle that is not composed of other particles. Elementary particles are the basic building blocks of matter and are the fundamental particles of nature. They include electrons, quarks, photons, and other subatomic particles. Elementary particles are not immutable and can change their state or form under certain conditions. For example, electrons can gain or lose energy by emitting or absorbing photons. Quarks can also change their flavor by interacting with other quarks through the strong nuclear force. Therefore, elementary particles are not particles with no change at all.