Fireflies and fungi have little in common, except that the fruiting bodies of some species of fungus have the ability to glow like firefly backsides. Chemists have known the structure of the luciferin molecule responsible for the firefly’s glow for more than 50 years. But they’ve had a hard time isolating enough of the luciferin molecule that lights up bioluminescent fungi to identify its structure. Now, thanks to chemists led by Ilia V. Yampolsky and Josef I. Gitelson of the Russian Academy of Sciences, this molecular mystery has finally been solved. The researchers found that 3-hydroxyhispidin, when mixed with oxygen and a luciferase enzyme present in bioluminescent fungi, bestows a luminous glow to fungal fruiting bodies (Angew. Chem. Int. Ed. 2015, DOI: 10.1002/anie.201501779). Hispidin—a common metabolite of fungi and plants—appears to be the fungal luciferin’s precursor. The 3-hydroxyhispidin luciferin is structurally distinct from the eight previously identified luciferin compounds, but it appears to account for the glow in four diverse genera of luminous fungi, suggesting a common biochemical mechanism for fungal bioluminescence.