The layer inside that touches the bottom of your feet is the spongy, soft insole. The top, or upper, is just as important. Your upper closes snugly with the help of laces tied over a protective tongue. Pieces of Velcro under fancy straps also hold shoes shut. Uppers are made of canvas, leather, man-made nylon, and plastics.
Leather is very strong.
Natural leather comes from cattle skins, or hides. These hides are mixed with salt and chemicals. They are dyed and dried, then squished into thin strips for sneakers. Man can make his own leather too. It is called synthetic leather and is used in many shoes.