Bioluminescence is the production and emission of light by a living organism. Bioluminescence is a form of chemiluminescence where light energy is released by a chemical reaction. Most deep sea (midnight zone: look at the picture above for reference) marine animals are bioluminescent. It can be used in nature for a variety of reasons, some being: mimicry, communication, distraction and warnings.
Seriously people this is an amazing part of nature that hasn’t really been explored. This Ted conference is really amazing and everyone should see it