Dreaming has intrigued humanity since antiquity, but its scientific exploration did not begin until 1953. At that time, sleep was commonly believed to be a passive, coma-like state. However, Aserinsky and Kleitman’s discovery of rapid eye movement (REM) sleep, and its link to brain activation and dreaming, revolutionized the field of sleep research.

This groundbreaking discovery began with an unexpected observation. In the early 1950s, Nathaniel Kleitman, a pioneer in sleep research, instructed his graduate student, Eugene Aserinsky, to study the behavioural correlates of falling asleep by observing infants. During these observations, Aserinsky noted substantial eye movements during infant sleep. Initially thinking these might be unique to infants, he was nevertheless motivated to develop quantitative methods to measure eye motility. After restoring an old electrical signal recording system, Aserinsky brought his 8-year-old son to the lab and placed electrodes near his eyes to test the prototype electrooculogram (EOG) recording. While his son slept, Aserinsky was astonished to see the ink pen track a sudden, back-and-forth, jerky swinging of eye movements, reminiscent of wakeful saccades. After repeating the observation, Aserinsky was certain that this was not due to any artefacts or errors; he had discovered something entirely new.