Everything is made out of molecules, including your palm and the wall next to you. If you put your palm on the wall, it won’t stick. You can pull it off very easily. But if you try the same thing with your finger, and attempt to pull it off of your hand, you can’t do it easily, and if you managed to do it you couldn’t put it back by just placing it there. What changed, and why do some molecules stay connected while others don’t?