A quite amazing paper has just appeared: Cells of a common developmental origin regulate REM/non-REM sleep and wakefulness in mice Mammalian sleep comprises rapid eye movement (REM) sleep and non-REM (NREM) sleep. To functionally isolate from the complex mixture of neurons populating the brainstem pons those involved in REM/NREM sleep switching, we pharmacogenetically manipulated neurons of a specific embryonic cell lineage in mice. We identified excitatory glutamatergic neurons that inhibit REM sleep and promote NREM sleep. These neurons shared a common developmental origin with neurons promoting wakefulness, both derived from a pool of proneural hindbrain cells expressing Atoh1 at embryonic day 10.5. We also identified inhibitory GABAergic neurons that act downstream to inhibit REM sleep. Artificial reduction or prolongation of REM sleep in turn affected slow wave activity (SWA) during subsequent NREM sleep, implicating REM sleep in the regulation of NREM sleep. Just a no...