From The School of Biomedical Sciences Wikiorganism. It is a form of chemiluminescence. Bioluminescence occurs widely in marine vertebrates and invertebrates, as well as in some fungi, microorganisms including some bioluminescent bacteria and terrestrial invertebrates such as fireflies.
Bioluminescence is a "cold light." Cold light means less than 20% of the light generates thermal radiation, or heat.