The ventrolateral preoptic nucleus (VLPO) in the brain plays a critical role in the initiation and maintenance of sleep, while the lateral posterior part of the hypothalamus contains neuronal populations implicated in maintenance of arousal. Now, a new study reveals that these arousal-related neurons are heavily innervated by GABAergic neurons in the preoptic area including the VLPO. The work provides important information to understand the mechanisms that control animals' sleep/wakefulness states.