Sleep research studies the physiological stages of sleep through controlled laboratory monitoring of brain activity, eye movement and muscle tone across a full night, distinguishing dreaming sleep from the deeper, dreamless stages that alternate with it. The discipline's founding discovery came in 1953, when the graduate student Eugene Aserinsky, working under Nathaniel Kleitman at the University of Chicago, identified rapid eye movement sleep by monitoring sleeping subjects overnight and correlating the distinctive eye movement pattern with vivid dream recall on waking, establishing for the first time that dreaming was tied to a specific, measurable physiological state rather than occurring unpredictably throughout sleep.
Dream visions and nighttime revelations feature across religious traditions as a claimed channel of divine or spiritual communication, and sleep research supplies the atlas with an independent physiological account of what is measurably happening during the sleep stage such experiences are reported in, without itself adjudicating whether a given reported vision carried genuine spiritual content. The atlas cites sleep research to describe the physiological state a dream vision occurred in, distinct from and alongside the religious significance a tradition assigns to that vision.