National Geographic:

Here is a story, for quarantined times, about extremely tiny organisms that do some of their best work by burping into uncooked dough. In the end, if things go well, there is good bread. If things go poorly, there is bad bread, or a mass of gluck you heave out so you can try again. This is the nature of yeast, which in its most familiar packaged version started vanishing from markets sometime in March, right after toilet paper and hand sanitizer.

Yeasts are single-celled creatures so complex and diverse that scientists have named only some of the many thousands of varieties living all around us. Yeasts live and reproduce in our homes, in our compost and sidewalk weeds, in our air, on our produce, on our skin.

And all the multiplying yeast bodies are eating sugar molecules they encounter in their surroundings. Yeasts like sugar. As they digest sugar, though, they discharge gases pungent enough to lift your bread dough, ferment your drink, and allow the kid in your household to examine a jarful of belching and flatulence.

I still remember as a kid my mother, a very accomplished baker, explaining what yeast was. “It’s alive!?” I exclaimed in horror. “I’m never eating your bread ever again!” That ultimatum lasted until the next delicious loaf came out of the oven.