After I’ve been outside playing all day, nothing feels quite as a good as a nice warm bath.

Sometimes I might even stay in the tub a little longer than usual, and when I /do/ finally get out, I notice that my fingers and toes are kind of ... wrinkly, or pruney, almost like a raisin! Maybe that’s happened to you, too, if you’ve been swimming for a long time, or even just doing some fun water experiments in the sink!

Have you ever wondered why that happens? Well, scientists have wondered that, too! And they’ve learned that it has a lot to do with what our skin is made of, and how water is so slippery.

Skin covers the whole outside of our bodies, and it’s pretty special stuff. Even though it’s hard to tell from the outside, skin is actually made up of layers, and each layer has different parts. Now, if we could look at the layers of our skin /very/ closely, they would look something like this.

There’s so much in there! We have something called vessels in our skin, which are the tubes that carry blood in our bodies. These vessels are /very/ small and thin, but they’re really important!

They can open up wide, or they can shrink down and kind of close up a little bit on the inside. That’s what happens when you’ve been wet for a long time — those tiny vessels shrink down. And when they shrink down, that big layer of skin they’re inside of gets a /little/ thinner.

When /that/ layer gets thinner, it causes the top layer of skin to relax and get a little looser. And that’s what causes the wrinkles! The top layer of skin is kind of like a piece of cloth.

When it’s pulled tight, it’s not wrinkled. But when it relaxes … it gets wrinkly! So that’s /how/ your fingers get wrinkly.

But /why/ do they get wrinkly — why does it help you to have wrinkly fingers and toes? Scientists don’t know for sure, but they’ve done /lots/ of experiments, and they think it’s to help you hold things better in the slippery water! During one experiment, a group of scientists asked people to soak their hands in water, and to let them get all wrinkled and pruny.

Then they asked the people with pruny fingers to try and pick up small, slippery objects underwater. Then they asked people who didn’t have wrinkly fingers to do the same thing. Well, it turns out that the people who had pruny hands could pick up the objects underwater /faster/ than the people who /didn’t/ have pruny hands!

It’s like the wrinkles on our fingers give us a special grip when it’s wet. Have you ever seen pajamas or slippers with bumps on the bottom of the feet? The bumps are there because they help keep you from slipping on the floor and falling down.

The wrinkles are kind of the same: they make your fingers more bumpy, which helps you hold onto things without them slipping through your fingers. So, as weird as pruny fingers and toes might look, they can be pretty useful! And once you dry off and wait a little bit, the vessels inside your skin open up again, and your skin goes back to normal — at least until the next time you take a long bath!

Thanks for joining us on SciShow Kids! We /love/ getting questions here at the Fort! So if you have any questions about our bodies, or anything at all, grab a grownup to help you leave a comment down below, or to send us an email at kids@scishow.com!