Narcolepsy serves as a prototype of how the interaction of high quality clinical research and groundbreaking basic science can collaborate to defne the cause of a disease and change forever how we evaluate and treat it. There is scarcely a topic in this book that would have been covered in the same way 10 years ago as it is d- cussed today. We are also fortunate that many of the players in this dramatic tu- around have contributed to this volume, so that the result is a tapestry of the events that have transformed the feld over the last decade that is both authentic and detailed. The frst section of the book provides much of the basic science background. As described in the frst two chapters, the dramatic convergence of lines of evidence from two different laboratories frst demonstrated in 1999 that narcolepsy is a disease of loss of neurotransmission by lateral hypothalamic neurons making the peptides that have been called orexins or hypocretins. These fndings did much to clarify and unify a feld that had puzzled for decades over the fundamental nature of this puzzling disease, as refected in the chapters that review its epidemiology and neuroanatomical and imaging fndings.