Although cellular metabolic (redox) state has long been associated with a housekeeping role, recent research from a team lead by Martha Gillette, and including the Lee Cox and Jonathan Sweedler groups, provides new insights on cellular redox states, linking them to the intrinsic daily (circadian) clock in the brain. In the August 17th issue of Science, T. A. Wang et al. show that redox states in this brain region reflect daily cycles of metabolism. This 24-hour metabolic rhythm regulates the electrical activity of the neurons that comprise the mammalian central circadian clock. Thus, cross talk between energetic and neuronal states enables cellular state to influence brain physiology.