Figuratively speaking, photons are what electromagnetic radiation is made of. The term “light particles” is also used frequently. Every electromagnetic radiation, from radio waves to gamma radiation, is quantised in photons. This means that the smallest amount of electromagnetic radiation of any frequency is a photon. Photons have an infinite natural life, but can be produced or destroyed by a variety of physical processes. A photon is never at rest but always moves at the speed of light. Therefore it has no rest mass.