Did you know you go on a journey every night after you close your eyes? Sleep scientist Matt Walker breaks down the difference between REM (Rapid-Eye Movement) and non-REM sleep, what occurs during each stage of sleep -- and why it's important to get enough of both.

Caffeine wakes you up, and alcohol makes you nod off, right? It's not that simple. Sleep scientist Matt Walker takes us into the eye-opening ways that these drinks affect the quantity and quality of our sleep.

We've all been told to get a good night's sleep before a test -- finally, here's the reason why. Sleep scientist Matt Walker explains how getting enough sleep affects how our brains store and process memories.

Does not getting enough sleep lead to Alzheimer's disease? Sleep scientist Matt Walker explains the relationship between the two -- and how researchers are exploring how to use sleep to decrease our chances of developing this condition.

It's not just your imagination -- you're more irritable when you're low on zzzzs. Sleep scientist Matt Walker explains how our nightly slumber affects the emotional centers in our brains, and why we can think of sleep as first aid for our feelings.

One of the best things that you can do to boost your immune system is head to bed, says sleep scientist Matt Walker. It can even make your flu shot more effective!

You know you need to get enough sleep, but the question remains: How much is enough? Sleep scientist Matt Walker tells us the recommended amount for adults and explains why it's necessary for your long-term health.

Want to not only fall asleep quickly but also stay asleep longer? Sleep scientist Matt Walker explains how your room temperature, lighting and other easy-to-fix factors can set the stage for a better night's rest.