Bioluminescence gets conflated with both fluorescence and phosphorescence. Bioluminencence is light emitted by living organisms. Fluorescence is the term for something that absorbs light energy from an external source and almost immediately re-emits it. When the external source is gone, it stops. Phosphorescence describes the absorption of light from an external source which slowly re-emits it. This would include glowing stickers. Bioluminescence results from a chemical reaction in the body of an organism. This can be a brain and nervous system response or can be triggered by a physical disturbance such as motion.
Bioluminescent organisms use forms of luciferin, which comes in many forms and gives off light when exposed to oxygen. There is also an enzyme, luciferase, which is a catalyst and speeds up the reaction.
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