Every night, while you lie still, your brain does some of its most important work.

Sleep is not the absence of life. It is, in a biological sense, some of life's most essential activity - consolidating the memories formed during the day, processing the emotional charge of difficult experiences, clearing the metabolic waste that accumulates in waking hours, and calibrating the hormonal systems on which long-term health depends.

Sleep: The Science of What Happens When You Rest draws on decades of neuroscience, psychology, and clinical research to explain, with precision and clarity, what actually happens across the eight hours of a night. You will discover how the brain cycles through distinct sleep stages with specific biological functions, why REM sleep is essential for emotional regulation and creative thinking, how the glymphatic system uses sleep to clear proteins linked to Alzheimer's disease, and why chronic sleep restriction has consequences that no amount of coffee or weekend recovery can reverse.

This book covers the complete landscape of sleep science: the architecture of a night's sleep, the circadian clock and what disrupts it, sleep's roles in memory and emotion, the spectrum of sleep disorders and their treatments, how sleep changes from infancy to old age, and what the evidence actually shows about sleeping better.

For everyone who has ever wondered what the night is actually for - and for everyone who suspects they are not getting enough of it.