What do you do at different times in the day? What do you eat? How do you interact with your neighbors? These are some of the questions that biologists would love to ask communities of microbes, from those that live in extreme environments deep in the ocean to those that cause chronic infections in humans. Now, a new technique developed at Caltech can answer these questions by surveying gene expression across a population of millions of bacterial cells while still preserving the cells' positions relative to one another.