Bioluminescence

How some enzymes produce light directly from a chemical reaction, with no illumination needed at all.

References

• Shimomura, O., Johnson, F.H., Saiga, Y. "Extraction, Purification and Properties of Aequorin, a Bioluminescent Protein from the Luminous Hydromedusan, Aequorea." Journal of Cellular and Comparative Physiology 59, no. 3 (1962): 223–239.