Bioluminescence, a form of chemiluminescence, is the production and emission of light by living organisms, including algae and phytoplankton, present in the oceans and in terrestrial fungi. Bioluminescence principally occurs when light-emitting pigments chemically react with enzymes and other proteins, and is not to be confused with fluorescence or phosphorescence, both of which do not involve a chemical reaction.
Rarely seen in fresh waters, but primarily occurring in marine environments, bioluminescence is the only source of light present in the deep sea; the largest habitable biome of the earth.
Common terrestrial manifestations of bioluminescence can be seen in flashing fire-flies, and glowing fungus on wood.
Bioluminescence is a beautiful example of biochemical phenomenon in nature.