How sleep actually works, and what the research says about sleeping well. Learn the stages of sleep and the roughly 90-minute cycle; the two-process model, in which sleep pressure (adenosine building up while you are awake) meets the circadian clock (the brain’s master clock, set each day by light and signaled by melatonin); chronotypes and how sleep changes from childhood to old age; how much sleep adults need and what deprivation does to attention, mood, memory and driving; how caffeine, alcohol and screens affect sleep; the routine and bedroom habits the evidence supports, and the parts of CBT-I (cognitive behavioral therapy for insomnia) such as stimulus control and a consistent wake time; shift work, jet lag and naps; and the common myths, from “catching up on weekends” to sleep trackers. Sleep disorders such as sleep apnea, restless legs and narcolepsy are taught as things to recognize and take to a clinician. Every explanation names the tempting myth and leaves you a rule. Distinct from Longevity (healthspan as a whole), Psychology and Neuroscience: this is the whole of sleep in one place. Educational only — not medical advice, and it does not diagnose or treat any condition.
• Meets you at your level — never too easy, never too hard.
• Adapts every question to how you’re doing.
• Tracks your level over time. Skill practice, not a test.
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