The method by which fireflies – alternatively known as lightning bugs – produce light is the best-known example of bioluminescence. Bioluminescence is the term used to describe the emission of cold, visible light by a living organism, such as the firefly. Most bioluminescent organisms live in the deep sea.
The video explains how bioluminescence works in the firefly and why it glows at all.
Aisha J. Syed, James C. Anderson, Applications of bioluminescence in biotechnology and beyond (Review Article), Chem. Soc. Rev. 2021, 50, 5668-5705. https://doi.org/10.1039/D0CS01492C
Thérèse Wilson, J. Woodland Hastings, Bioluminescence, Annual Review of Cell and Developmental Biology 1998, 14, 197-230. https://doi.org/10.1146/annurev.cellbio.14.1.197