A scanning electron microscope picture of a nerve ending. It has been broken open to reveal vesicles (orange and blue) containing chemicals used to pass messages in the nervous system. Credit: Tina Carvalho, University of Hawaii at Manoa.

A scanning electron microscope picture of a nerve ending. It has been broken open to reveal vesicles (orange and blue) containing chemicals used to pass messages in the nervous system. Credit: Tina Carvalho, University of Hawaii at Manoa.