Think of the firefly abdomen like a black box of bioluminescence. For around 60 years, scientists have known what basic ingredients go into the box - things like oxygen, calcium, magnesium, and a naturally occurring chemical called luciferin. And they've known what comes out of the box - photons, or light, in the form of the yellow, green, orange, and even blue flickers you see dancing across your backyard on summer nights.
But until recently, the actual chemical reactions that produce the firefly's light have been shrouded in mystery. Now, that mystery has been solved.