Colour scanning electron micrograph of a neuromuscular junction showing a motor neurone (pink) terminating on skeletal muscle fibres. The axon of a motor neurone terminates in several branching fibres, each of which ends in an end plate, a cluster of small swellings or boutons. When activated, the boutons release neurotransmitter chemicals from small vesicles, which diffuse across the gap (the synapse) separating the cells to interact with receptors in the muscle cell. Magnification: x660 at 6x7cm size, x330 at 35mm size.