Earth is a diurnal planet − a world of day and night. Accordingly, countless species − from the simplest of organisms to the most complex − have evolved in such a manner that they are attuned to this daily cycle of light and dark. From microbes and insects, to animals and humans, entire ecosystems dance to the rhythm of our revolving planet. As the sun goes down, myriad insects commence their pollinating duties. Migrating birds navigate by the light of the moon and the stars; hatchlings of sea turtles scurry to the sea when they make out the faint glow over the horizon; humans are lulled to sleep when darkness falls and the hormone melatonin is secreted.