In the twentieth century, dreams were demysti ed by focusing on the measurable neurobiological impact of dreaming, especially on memory processing and consolidation. Scienti c studies attest to the role of REM sleep (when dreaming occurs) in memory processing and consolidation, particularly in emotionally charged memories. Behavioural studies of sleep and learning in both animals and humans attest to the neurobiological and neurophysiological basis of sleep-dependent memory processing. Chronic nightmare su erers, sleepwalkers and narcoleptics today can turn to medical professionals for treatment such as nightmare imagery rehearsal therapy, diet changes, stimulants, anti-depressants, and more. But, how were dreams and nightmares treated in other historical times and places? How were dreams and nightmares de ned and di erentiated from one another? How were dreams and nightmares dealt with in late Ming China (1368-1644)?