Researchers studied how magic mushrooms (Psilocybe mexicana) regulate their chemistry to produce psilocybin, the psychoactive compound. They found that when mushrooms start fruiting, they turn on genes that make tryptophan (an amino acid building block) and turn off genes that break it down, directing all the tryptophan toward psilocybin production. This coordinated genetic control ensures the mushroom has enough of this key ingredient. This knowledge could help grow these mushrooms in labs for legitimate medical research into treating depression.