Luciferin is a molecule that when broken down in fireflies produces heat and light the rate at which luciferin is broken down in cells is controlled by

Bioluminescence is the phenomenon of production and emission of light by living organisms. The classic example of bioluminescence is the firefly. They produce light in specialized light-emitting organs present in its lower abdomen. The substrate for the production of the light is the luciferin which is acted upon by the enzyme luciferase in the presence of magnesium ions, ATP and oxygen. The yellow light produced by the light-emitting compound called the firefly luciferin is controlled by the oxidative enzyme luciferase. The enzyme converts the luciferin into oxyluciferin. Oxyluciferin is a highly unstable compound that emits light upon relaxation to its ground state.