Everything you ever wanted to know about sleep but were too exhausted to ask. We spend around a third of our lives sleeping. But what actually happens during those hours? This book takes you on a fascinating journey through the land of nod and out the other side. •    What are circadian rhythms and how do they affect our energy levels throughout the day? •    What are dreams for and how do they happen? •    What are the different stages of sleep? •    Do animals experience sleep the same way we do? With clear texts and bright, distinctive illustrations, this is a great introduction to a subject that has fascinated us since ancient times, and an engaging tie-in to biology and natural sciences curriculums.