Not all genes are driven by the clock. Some do the same processes, producing the same chemicals, all the time. But half of your genome—the genetic information in your body—is regulated by your body clock. That can have important implications, especially for medicine. Studying different kinds of animals has produced databases of how their body clock affects different kinds of tissues in the body. But until now, there’s been no such database for humans—and no explicit confirmation that half our genome, as with other mammals, relies on the clock. In this study, “we were interested in identifying the molecular rhythms of different human tissues,” first author Mark Ruben says. They reported back on 13 different types of human tissue, including colon, thyroid, and several different heart tissues.