It had long been a quandry how geckos can walk on vertical surfaces without falling off. Their toes are not sticky, and their claws do not grip the surface as they can walk on glass as well.
Electron microscopy has shown that the pads of their toes are covered with tiny hair-like projections. This provides a large surface area in contact with the substrate, and they adhere due to "Van der Waals forces", that attract two substances in very close approximation. This involved quantum mechanics to fully understand. I am not making this up.