Every memory, from our first recollection of a family event, to our response to the ring of a doorbell, defines who we are. Without memory constantly linking the threads of our present, past and future, we would not have a personal history, or know how to think or behave. But why, if remembering is so ordinary, do we momentarily forget the name of a loved one, or struggle to find an answer that we think we know? Are our memories fixed in particular chunks of brain tissue, or is memory a dynamic, biologically creative process that involves many different parts of the brain? How long do different memories last? And what do genes contribute to the process?