The bodies of some living organisms like fireflies and glowworms- are able to give off visible light. This phenomenon is known as bio luminescence. Glowing animals create light by mixing chemical compounds in their bodies to produce light. This ability to produce light is most common among insects that fly at night, as they use light to communicate.
In the depths of the ocean, there us no natural light; so many deep-sea fish produce their own light. The angler fish and the flashlight fish have special light- producing bacteria in their bodies. The angler fish has a spine with a bulb at the end that it dangles in front of its mouth. It can switch the glow on and off by increasing or reducing the flow of blood to the bulb.