We do a pretty good job at appreciating the visible intricacies of nature: the antennae and legs and claws of a lobster, the geometrical order of the spots on a butterfly’s wings. But a lot of nature’s intricacies are hidden away inside single-celled creatures, such as the baker’s yeast that makes bread rise and beer ferment. At an audition for a David Attenborough documentary, a yeast cell guzzling away on sugar is bound to do a lousy job. (“Thanks, don’t call us; we’ll call you. Send in the King Cobra!”) But the intricacy of its metabolism is no less impressive. What’s more, scientists know how to manipulate yeast in ways they can’t with animals, and that power lets them set