Dream

A dream is a succession of images, dynamic scenes and situations, ideas, emotions and sensations that usually occurs involuntarily in the mind during certain stages of sleep; humans spend more than two hours dreaming per night, and each dream lasts around five to twenty minutes. The content and function of dreams have been subjects of scientific, philosophical and religious interest throughout recorded history, and dream interpretation, practiced by the Babylonians in the third millennium BCE and even earlier by the ancient Sumerians, figures prominently in the religious texts of several traditions and has played a leading role in psychotherapy; the related practice of dreamwork is similar but does not seek to conclude with a single definite meaning. The scientific study of dreams is called oneirology, and most modern research on the subject focuses on the neurophysiology of dreams and on proposing and testing hypotheses about their function, though it remains unknown where in the brain dreams originate, whether they have a single origin or involve multiple brain regions, or what purpose dreaming serves for the body, brain or mind.