HA22 is an EM of a neuromuscular junction (NMJ) that shows the elaborate structure of this contact point of a motor neuron and its target. The membrane surface area is increased in several ways to ensure effective cell signaling. The motor neuron axon terminus branches many times (HA21). These termini sit in folds called primary synaptic clefts. Multiple membrane folds called secondary synaptic clefts come off of the primary clefts. To maintain insulation, Schwann cells sit on top of the axon termini, but do not intervene between the two cells. Muscle nuclei sit close to the NMJ and support production of the NMJ molecular components. Mitochondria provide ATP to both the membrane channels and myofilaments.