Talk:Fila-mint/@comment-24638751-20180502090710/@comment-33492460-20180508195117

Spontaneous emission is the process in which a quantum mechanical system (such as an atom, molecule or subatomic particle) transitions from an excited energy state to a lower energy state (e.g., its ground state) and emits a quantum in the form of a photon. Spontaneous emission is ultimately responsible for most of the light we see all around us.

Straight from wikipedia.

Basically, to produce photon, i.e light, it require the electrons in the atoms of an material to change energy state. Movements of electrons make light.