How does Velcro stick and unstick?

Velcro sticks because one strip has tiny hooks and the other has tiny loops. When pressed together, many hooks catch many loops, making a strong hold; when you peel from an edge, the catches release a few at a time.

The clever idea came from burrs that cling to coats and fur after a walk outdoors. Look closely at those prickly seeds, and you find little natural grappling shapes that inspired fasteners for shoes, bags, medical cuffs, and even space gear.