Explore how bioluminescence works in this video from NOVA: Creatures of Light. Organisms, such as fireflies, emit light produced from a chemical reaction. The key chemicals involved in bioluminescence are luciferin (which acts as a fuel) and luciferase (which acts like a spark). When luciferin and luciferase are mixed together with oxygen and other ingredients, the chemical reaction produces energy in the form of light. Bioluminescence has evolved independently more than 40 separate times along different lineages in the tree of life. The actual luciferins and luciferase enzymes involved differ from creature to creature, but the basic mechanism of light production is the same. This resource is part of the NOVA Collection.