Which experience led an engineer to invert velcro

De Mestral first conceptualized hook and loop after returning from a hunting trip with his dog in the Alps in 1941.After removing several of the burdock burrs (seeds) that kept sticking to his clothes and his dog's fur, he became curious as to how it worked. He examined them under a microscope, and noted hundreds of "hooks" that caught on anything with a loop, such as clothing, animal fur, or hair. He saw the possibility of binding two materials reversibly in a simple fashion,if he could figure out how to duplicate the hooks and loops.

Active site is where they touch.