When your fingers and toes get pruney, they develop temporary wrinkles and ridges after being in water for a while. If you've ever taken a long bath or spent an afternoon swimming, you've probably noticed your fingertips looking like tiny mountain ranges with valleys and peaks. The skin puckers up and feels different to the touch, sort of soft and textured at the same time.

Scientists used to think this happened simply because skin absorbed water and swelled up, like a sponge. But researchers discovered something more interesting: your body actually does this on purpose. Your nervous system makes the blood vessels in your fingertips constrict, pulling the skin inward to create those wrinkles. Why? The wrinkles work like tire treads, giving you better grip on wet or slippery objects. It's your body's clever way of helping you hold onto things when everything's wet.

The effect is temporary. Once you dry off and spend some time out of the water, your fingers and toes return to normal within minutes. People call it pruney because wrinkled fingers look a bit like dried prunes.