For most of the twentieth century chemists thought onion tears were an accident. Cutting an onion breaks its cells, an enzyme called alliinase meets the sulfur compounds it had been kept apart from, and the stinging gas was supposed to fall out of that reaction on its own, the way sawdust falls out of sawing. Then, around 2002, Shinsuke Imai and his colleagues at House Foods in Japan tried to make the gas in a dish, using onion compounds and alliinase taken from garlic. Nothing happened. Garlic has alliinase too, and garlic has never made anybody cry. The missing piece turned out to be a second enzyme, which onions have and garlic doesn’t, whose only known job is to turn the sawdust into the sting. So it was never an accident. The onion spends a whole enzyme on it. The experiment that found this was the one that failed, and in 2013 it won an Ig Nobel Prize for showing that crying over onions is more complicated than anyone had thought.