In the deep ocean, where sunlight cannot reach, an extraordinary proportion of organisms produce their own light. Bioluminescence — the emission of light through chemical reactions — is found in at least 1,500 species of fish and countless invertebrates. The chemical reaction typically involves a light-emitting molecule called luciferin and an enzyme called luciferase. Organisms use bioluminescence for communication, predation (the anglerfish's glowing lure), defense (ejecting luminous fluid to confuse predators), and camouflage (counter-illumination to match downwelling light).