Whether invertebrates display distinct sleep stages, similar to those seen in mammals, is unknown. Yap et al. recorded local field potentials from the brains of flies during sleep and observed the presence of an intermittent 7–10 Hz oscillation that was associated with transitions between sleep and wakefulness. They further showed that the dorsal fan-shaped body of the central brain is responsible for generating these oscillations. These findings thus provide neural evidence for sleep stages in flies and provide insight into the underlying mechanisms.