Sleep and wakefulness undergo important changes with age. Awakening, a crucial event in the sleep-wake rhythm, is a transition implying complex physiological mechanisms. Its involvement in sleep disturbances is also well known. This collective volume is the first attempt to systematically approach awakening across development.A methodological section considers criteria to define awakening in a developmental perspective. Theoretical considerations on development of wakefulness and on its relation to consciousness are included and provide a vigorous impulse to go beyond present criteria and classifications. Age changes are the core of studies on development: a section of the book examines old and new data from preterm to infants up to children, underscoring the main turning points along this developmental path. As for other aspects of development, awakening and the sleep-wake cycle are also influenced by external factors, both physical and human. Several contributions deal with this topic, in particular focusing on the parent-infant interaction and the influences of culture. Clinical contexts offer an opportunity to show both quantitative and qualitative changes of awakening and arousals in different pathological conditions. Either partial changes of one physiological variable or global and massive changes can be observed. (Series B)