Photon emission is the process by which a photon, a particle of light, is released from an atom or molecule. This occurs when an electron in a higher energy state transitions to a lower energy state, releasing energy in the form of a photon. The energy of the emitted photon corresponds to the difference in energy levels of the electron. This phenomenon is fundamental in various fields, including quantum mechanics and optics. It is responsible for the light produced by sources such as lasers and LEDs, and plays a crucial role in processes like photosynthesis in plants, where light energy is converted into chemical energy.