All around the world, oceans glow and trees sparkle because of Bioluminescence, the production of light by living organisms.
Bioluminescent creatures have a chemical reaction in their body that creates light. The chemical Luciferin (a substrate) reacts with Luciferase (an enzyme) to create a by-product called Oxyluciferin. or as we see it; Light.
In this gif, Aequorea victoria/Crystal Jellies thrive in deep sea.