The phenomenon of chemiluminescence is largely used in analytical chemistry.

Chemiluminescence is produced by a chemical reaction that emits light, but no significant quantities of heat. An example of chemiluminescence are the popular glow sticks. This differs from fireflies, which get their glow instead from bioluminescence.

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Chemiluminescence is the name of a system of glowing. Example- the name of the system on how glow sticks glow is called chemiluminescence. But in living things, such as fireflies it is called luminesence.

For a firefly, the function of chemiluminescence is to attract a mate. For some deep ocean creatures it is used to attract prey. For other applications see:

http:/en.wikipedia.org/wiki/Chemiluminescence