The single most effective sleep hack costs nothing: morning sunlight within 30 minutes of waking.

Andrew Huberman's most-shared advice isn't a supplement or a gadget — it's getting bright light in your eyes within 30 minutes of waking up. Go outside. Face the sky (not directly at the sun). 5-10 minutes on a clear day, 15-20 minutes on a cloudy one.

Why? Your circadian clock — the master timer for sleep, hormones, and metabolism — is set primarily by light hitting your retina. Morning light triggers a cortisol pulse (healthy, not stress cortisol) that starts a 12-14 hour countdown to melatonin release. Get morning light at 7am, and your body knows to start producing melatonin around 9-10pm. Skip it, and your clock drifts.

This one habit fixes the most common sleep complaints: difficulty falling asleep, waking up groggy, and inconsistent sleep timing. It's more effective than melatonin supplements because it programs your own melatonin production at the right time.

The upgrade: get evening light too. Watching the sunset (or being outside in low light in the evening) tells your clock that darkness is coming, making the melatonin transition smoother. And after sunset, dim indoor lights and avoid overhead lighting — it signals "daytime" to your brain.