<p>Historically, it was Constantin von Economo who first identified sleep-associated brain regions, linking lesions in the anterior hypothalamus to insomnia. Later experimental work in animals confirmed the preoptic area’s (POA’s) role in sleep regulation. The medial preoptic area (mPOA), lateral preoptic area (lPOA), and other hypothalamic and brainstem regions are involved in sleep –wake control, thermoregulation, and other homeostatic processes. Notably, lesion studies disrupting various parts of the preoptic region produce significant alterations in sleep architecture, but do not abolish sleep entirely, underscoring its autoregulatory and global nature. Some studies, primarily based on early neurophysiological and neurochemical investigations, emphasized the central role of the ventrolateral preoptic area (VLPO) in initiating and maintaining sleep. Information available on the rest of the POA shows that the mPOA is important for sleep maintenance. The surrounding areas, including lPOA and VLPO, play a role in sleep initiation. Modern functional imaging supports the concept that sleep regulation involves widespread brain networks that dynamically interact during different sleep stages. Recent research identifying salt-inducible kinase 3 (SIK3) as a key sleep-regulating gene provides further evidence for the global nature of sleep regulation, as SIK3 is ubiquitously expressed in the brain. Thus, defining the VLPO as the sole “sleep center” is not only erroneous but it also oversimplifies a highly integrated, multi region system. Sleep regulation is a complex emergent property of a widespread neural circuit, with the POA serving as a key component<b>.</b></p>