Sleep

What is sleep? Why do we dream? And how does it change as we get older? Sleep is a fundamental biological process, yet scientists are uncovering what happens when we close our eyes. Good-quality sleep is essential for almost every aspect of human health – from brain function and immunity to physical repair and mental well-being. Too little can affect everything from mood to susceptibility to illness. This lively guide traces our understanding of sleep, from how our ancestors slept to modern habits, and offers practical tips for a better night’s sleep.