If you need to climb trees and hang sideways to a leaf or branch, like tree frogs often do, you need a way to both stick and unstick to things.
Tree frogs do this with their unique toes. Up close, each toe is divided into hexagon-shaped (six-sided) pads, separated by narrow channels. When they lift their feet, sticky mucus flows out of the channels and
across their toe pads, making sure they stick when they put their foot down. But when they lift their foot to take another step, the mucus drains away through those same channels, cleaning off their toe pads and making them
ready for new mucus. In other words, the toe
pads of tree frogs are designed to clean themselves continuously as they move, making sure they stick securely with each new step or hop!