@RickiTarr Luciferase is the generic term for the substrate and enzyme that result in #bioluminescence in a number or organisms. Luciferase genes can be synthesized in the lab through #genetic engineering and inserted into organisms or transfected into cells. It is used in the “action” part of a synthetic molecular switch to provide evidence that the switch worked. The Wikipedia article is a decent explainer. In addition to the applications it mentions, it has been used in pigs and rabbits.