Synesthesia comes from the Greek <i>syn</i> (meaning union) and <i>aisthesis</i> (sensation), literally interpreted as a joining of the senses. Synesthesia is an involuntary joining in which the real information from one sense is joined or accompanies a perception in another. Dr. Cytowic reports extensive research into the physical, psychological, neural, and familial background of a group of synesthets. His findings form the first complete picture of the brain mechanisms that underlie this remarkable perceptual experience. His research demonstrates that this rare condition is brain-based and perceptual and not mind-based, as is the case with memory or imagery. <i>Synesthesia</i> offers a unique and detailed study of a condition which has confounded scientists for more than 200 years.