The pioneering work of Jeffrey Hall, Michael Rosbash, and Michael Young transformed the field of molecular biology by revealing the gene-driven mechanism that controls circadian (daily) rhythms in the nervous system. Through painstaking research, they established that the circadian rhythms of the fruit fly (Drosophila) are run by a transcriptional negative-feedback loop. They also uncovered many of the interacting genes and gene products that control this mechanism, including a light-sensing protein that uses the day/night light cycle to help synchronize daily behavioral cycles to natural environmental cycles. Subsequent studies by others have demonstrated that these discoveries apply not only to fruit flies, but also to mammals, including humans. Biological rhythms are now understood to play a crucial role in how the human brain—and body—functions.