Today is World Sleep Day—yes, that’s actually a thing that exists. World Sleep Day is an annual event aiming to help build awareness of the benefits and importance of getting good sleep, improving your sleep hygiene, and using sleep to enhance your overall health. After all, we spend about a third of our lives asleep on average!

What you might find surprising, however, is that there’s far more to learn about getting the best possible sleep than you thought. Here are seven fun sleep facts you might not know.

1. Bed head: why does our hair stick up after we sleep?

One of the most common pitfalls of waking up is when your hair becomes sticky, disheveled, and cow-licked, causing you to look at your mirror in horror and dread. Otherwise known as “bed head”, this is the result of you moving around in different positions during sleep. which leads to weight being added onto certain parts of your head—and the hair on those areas sticking up.

2. Do horses sleep standing up? Yes and no.

Though horses don’t fully go to sleep whilst upright, they do nap in that position. Horses have a network of muscles and ligaments known as the “stay apparatus”, which keeps them standing up without falling by keeping their joints locked while they’re dozing off. This is also to avoid being eaten by predators, since horses are slow to get up after lying down.

3. As for sharks? Yes—they do sleep after all

While it might not be obvious, sharks do need rest from time to time. In fact, they’re capable of sleeping while their eyes stay open. This mostly depends on the type of shark, however. Some need to forgo sleep to swim around and hydrate their gills—necessary for them to keep their oxygen levels up. Other types of sharks are able breathe while they’re resting, since they have spiracles to bring water through their gills without needing to swim.

4. Want to optimize your sleep routine? Try meditating.

A 2020 study from Harvard University indicates that practicing mindfulness meditation has been shown to make people feel more relaxed before bedtime. You can practice it before while listening to ambient music suitable for meditation. When you meditate, your parasympathetic nervous system activates—leading to your heart rate going down.

5. REM sleep: which part of the brain makes that happen?

This type of sleep—short for “rapid-eye movement”—is the one where you dream most often. How does this happen? The brainstem contains neurotransmitters that are critical for the regulation of REM sleep. Though you only spend a quarter of your sleep in REM, your brain activity goes up in ways that are very similar to when you're awake.

6. Elevating your legs while you sleep? Not as weird as you think

Lying down with your legs up promotes blood flow, helps relieve back pain, reduces swelling in your legs and feet, and prevents blood clots from forming in your extremities (better known as deep vein thrombosis). The latter is especially a risk if you’ve spent too much time not moving your legs.

7. Sleeping on the couch can get you sleeping faster than a bed

Hard as it may be to believe, this is a common pattern. Why? Because if we find ourselves frequently falling asleep on a sofa, our brains get used to this and associates the couch with bedtime. Though it isn’t an insomnia cure by itself, the patterns formed in our brains from sleeping on the couch can make it hard to sleep comfortably while in bed.