This book summarizes the results of a revolution in the scientific understanding of memory, mind, and brain that began in 1953 when a twenty-seven-year-old man underwent brain surgery to remedy life-threatening epilepsy. His name was Henry Moliason, but until recently, the general public knew him only as H.M. Henry's operation inadvertently destroyed his hippocampus, the brain's engine for forming new memories. He suffered catastrophic memory failures for the rest of his life. Henry soon became the most studied amnesiac patient in the history of the world and also the most famous. Dr. MacKay worked with Henry for fifty years. This book focuses primarily on the lessons of the still ongoing revolution that Henry inspired for readers wishing to maintain the everyday functioning of their memory, mind, and brain. The research done with Henry has shown how to keep memory sharp at any age and acquire ways to offset the degradation that aging and infrequent use inflict on memory. It has also given scientists insights into the different types of memory-- for example, memories of events, facts, skills, words, and visual experiences-- and the likelihood of forgetting each type of memory. Finally, it has revealed the profound importance of memory- memory decline impacts even such seemingly unrelated aspects of mind as the ability to plan, to comprehend, to detect and correct errors, to appreciate humor, to perceive the visual world, to imagine hypothetical events, and to create novel ideas. Written in an accessible style, this engaging narrative combines personal vignettes into Henry's life with important new findings about memory and brain functions.