luciferin

Luciferin is a molecule found in organisms that produce bioluminescence, meaning they can glow in the dark. It serves as the "fuel" in the light-producing chemical reaction. When luciferin reacts with an enzyme called luciferase, and usually in the presence of oxygen, it emits light through a chemical transformation. This process is common in many marine animals, fungi, and some insects like fireflies, and they use it for communication, attracting prey, or camouflage. In short, luciferin is the natural substance that enables these creatures to produce their characteristic glow.