How Your Circadian Rhythm Actually Controls When You Feel Sleepy
Your internal 24-hour clock decides when you feel alert or drowsy. Learn how light, the SCN, and melatonin set your circadian rhythm every single day.
Topic
How sleep really works — circadian rhythm, sleep stages and what the research does (and doesn't) actually say.
Your internal 24-hour clock decides when you feel alert or drowsy. Learn how light, the SCN, and melatonin set your circadian rhythm every single day.
Sleep debt accumulates fast but repays slowly. Learn what a night of lost sleep really costs and whether weekend catch-up can ever square the account.
Night owl, morning lark, or somewhere between? Discover how your genetic chronotype shapes your ideal bedtime, peak focus hours, and social jet lag.
Deep sleep repairs your body while REM consolidates memory and mood. Learn which stage matters more, how much you need, and what happens when you skimp.
Melatonin is your body's darkness signal, not a sedative. Learn when it naturally peaks, how light suppresses it, and why timing beats dosage.
Sleep pressure builds from the moment you wake as adenosine accumulates in your brain. Here is how it works and why caffeine only borrows time from it.
During REM your brain is nearly as active as when awake, yet your body is paralyzed. Explore what dreaming, memory, and emotion do during this stage.
From light N1 drifting to deep slow-wave sleep and vivid REM, here is what each stage of a sleep cycle does for your brain and body while you rest.