Sleep can be viewed as a brain state, as a process and a behavior. As any of these, sleep serves several purposes, including energy restoration, immunocompetence, brain metabolic homeostasis, neural ontogenesis and, importantly, cognitive, emotional and social processing. Supported by a strong empirical backbone focused on contemporary research outlining links between these subjects, this book will offer a guide to state-of-the-art research of sleep mechanisms, its impact in many cognitive and affective features as well as brief but in-depth overview of the strong association between sleep and social interactions. The complexity behind the common mechanisms between sleep, cognition and emotion, reveal that only through an integral approach in its study at both a neuroanatomical, functional, clinical and social level can reveal how this interplay influences human and furthermore, of mammal homeostasis as whole. Also, we intend to shed a light on the complex relationships between sleep and specific psychiatric disorders, thereby informing both prevention and clinical intervention. In order to provide clear guidance for researchers, the book also outlines future directions for the continued advancement of our understanding of sleep. We aim to balance the breadth and depth of available information to provide a resource that is accessible for upper-level seminars within academic settings, while serving as a practical guide for established scholars studying and treating conditions related to the interplay between sleep, cognition and emotion.