Researchers identified neurons that promote non-REM sleep in the brainstem in mice. These neurons commonly expressed the gene that encodes the neuropeptide neurotensin. Activation of these neurons induced non-REM sleep. Moreover, direct administration of neurotensin into the ventricle induced NREM sleep-like brain activity. These findings contribute to our understanding of sleep promotion and sleep disorders, and could tell us more about the evolution of sleep architecture in mammals.