Dedicated neuronal circuits mediate execution, choice, and coordination of body action Movement is the most common final output of nervous system activity and is essential for survival. But what makes this seemingly trivial statement so scientifically challenging? Neurons that contribute to when and how our body moves are distributed throughout the nervous system. Thus, even a simple movement such as arm flexion requires the coordinated activation of many different neuronal populations across multiple brain regions. A key question is how the nervous system produces diverse and precise actions aligned with the organisms' behavioral needs. These processes are affected in diseases such as Parkinson's or Huntington's, in which aberrant motor behavior dominates. Recent studies are transformative in how we think about the control of movement. A common denominator of these studies is that brain regions that contribute to motor behavior can no longer be considered as interacting boxes. Instead, deep circuit-level insight based on specific neuronal populations emerges as being critical to revealing motor system organization and understanding its function. It is likely that insights at this level can also help to design more specific and direct interventions for diseases of the motor system and neuroprosthetics applied after injuries.