Motor units are functional units in the nervous system that consist of a motor neuron and the muscle fibers it innervates. When a motor neuron fires, all the muscle fibers in its motor unit contract simultaneously. Motor units play a crucial role in coordinated muscle movement and are essential for voluntary and involuntary movements in the body. Research in this area often focuses on understanding the organization and recruitment of motor units, as well as the mechanisms underlying muscle contraction and motor control. Studying motor units can provide insights into neurological disorders, muscle diseases, and the effects of aging on muscle function.