When a substance emits light which is not a result of heat, then such a spontaneous emission fo light is known as luminescence.
Several chemical reactions or electrical energy can lead to the production of luminescence by organisms.
The enzyme that is responsible for the production of bioluminescence by the organism is luciferase and it is capable of producing luminescence by catalyzing oxido-reductive processes.
Luminescence is also produced in bacteria, and it is often controlled by the process of quorumsensing.