This chapter begins with the integrative process that transforms a succession of fleeting and discontinuous retinal snapshots into a stable perceived world. The symbolic function of imagery and dreaming is considered, along with "dream-incorporation" and related phenomena. Schizophrenic, hypnotic, and drug-induced hallucinations are discussed. An ingenious demonstration by shows that this kind of visual memory can be more powerful than mere set in determining how an ambiguous figure will be organized; The subject of eidetic imagery has recently been revived in a careful study by Haber and Haber, noteworthy both for its method and for its results. The Haber's relied systematically on a criterion which had been used only haphazardly in the classical eidetic work: eye movements. The images occasionally produced by electrical stimulation of the brain have been described as very different from the others that have considered. Many have used electrical and eye-movement criteria to identify the dreaming sleep, and improved dream recall by awakening the subject immediately.