The yeast that has been used for millennia to brew alcoholic drinks has now been engineered to produce cannabinoids — chemicals with medicinal and mind-altering properties found in cannabis. The feat, described in Nature, turns a sugar in brewer’s yeast called galactose into tetrahydrocannabinol (THC), a main psychoactive compound in cannabis. The altered yeast can also produce cannabidiol (CBD), a cannabinoid with potential therapeutic benefits, including its anti-anxiety and pain-relief effects. This fermentation process will enable manufacturers to produce THC, CBD and other rare cannabinoids more cheaply, efficiently and reliably than conventional plant-based cultivation. (See also: A cannabis high, no plant required)