I was watching a film in my behavioral neuroscience class yesterday and it showed a connection between neurons forming. (not an animation, this was filmed using a microscope) You could actually see an axon and dendrite moving closer and closer together. Then when they got close enough they started doing this handshake-like pumping motion. It was fascinating to watch. Anyway, my question is: what draws an axon and dendrite toward each other? Is it charge?