By the mid-1950s, it was apparent that neurons communicated with each other via chemical synapses. Electron microscopy experiments revealed that neurotransmitters were released from membranous vesicles stored in the nerve endings, as seen in the accompanying electron micrograph (middle and right) (copyright 1973 Rockefeller University Press. Originally published in Journal of Cell Biology. 57:315–344. doi: 10.1083/jcb.57.2.315; ref. 8). It took 40 more years to elucidate the molecular mechanisms that govern neurotransmitter release.