Sleep Science

Every Sleep Science article on Fall Asleep Tonight, newest first.

Groggy After a Full Night's Sleep? That's Sleep Inertia, Not Bad Sleep

Groggy After a Full Night's Sleep? That's Sleep Inertia, Not Bad Sleep

2026-07-13

That thick fog for the first 20 minutes after waking has a name and a real physiological cause, and it says almost nothing about how well you slept the night before.

The First 90 Minutes of Sleep Do the Heaviest Lifting

The First 90 Minutes of Sleep Do the Heaviest Lifting

2026-07-09

A bad start to the night costs you more than a bad middle or end does, and your sleep tracker's deep sleep graph probably isn't broken, even when the number looks low.

Why Some People Need 9 Hours of Sleep and Others Feel Totally Fine on 6

Why Some People Need 9 Hours of Sleep and Others Feel Totally Fine on 6

2026-05-24

The 8-hour rule was never based on individual biology in the first place. Why sleep need varies so much between people, and how to figure out your own real number.