The observation that cycles of sleep and wakefulness occur with a periodicity fixed in time to
match the rotation of the Earth on its axis provided a key to unlock the first genetic code for a
neurobehavioral pathway in flies and ultimately in mice. As a remarkable outcome of this
discovery, we have gained an unprecedented view of the conserved genetic program that
encodes a sense of time across all kingdoms of life. The tools are now in hand to begin to
understand how important processes such as energy homeostasis and fuel utilization are …