Humans have relied on microbes for millennia. Yeast brews our beer and raises our bread. Bacteria in our guts keep us healthy. Microscopic phytoplankton in the ocean produce half of the world’s oxygen. Thanks to genetic engineering, technology, and good old evolution, humans are about to enter into a new phase of our ancient partnership. We may soon create bacteria that eat plastic, emit light, and even tell us whether or not we’re healthy. When it comes to microbes, big things come from small packages.