A zymogene is a microorganism that causes fermentation — from the Greek zyme, leaven, and genes, born. Yeasts that turn grape juice into wine, lactic acid bacteria that turn milk into yoghurt, and the moulds of soy sauce and tempeh are all zymogenes: living agents whose metabolism transforms raw materials. The term belongs to the older vocabulary of fermentation science, where the discovery that fermentation was the work of living microbes — not spontaneous chemistry — was revolutionary. Modern usage prefers specific names — yeast, LAB, starter culture — but zymogene usefully names the category: the tiny workers behind bread, beer, cheese, and all fermented foods. Without zymogenes, human cuisine would be unrecognisable.