The newest science teaches us that nature has been keeping a secret — or a secretion, to be specific. It turns out that a newly discovered receptor in the eye, one that senses blue light in varying quantities and sends adaptive messages to the brain, also signals the release of the hormone melatonin. Melatonin in turn signals the body that it’s time to kick back, chill out, calm down, and get ready for sleep. Too much too soon — or too late — and our bodies lose their way in the world.