Bioluminescence

Bioluminescence, the production of nonthermal light by living organisms, such as fireflies, many marine animals, bacteria, and fungi. The effect is an example of chemiluminescence. In some cases its utility to the organism is not apparent, though in others its use is clear: In the firefly, the abdomen of the female glows, enabling the male to find her; similarly, luminescence enables many deep-sea fish to locate each other or to attract their prey. The glow in a ship's wake at night is due to luminescent microorganisms.