Remarkable diversity of neuronal identity and positioning in the nervous system generates a rich repertoire of animal behaviors, but poses a challenging question: how such neuronal identity and position are translated into wiring diagram of neural circuits? In this lecture, we look into an evolutionarily conserved spinal reflex circuit that assembles in an activity independent-manner and, therefore, is defined genetically. The authors of this article discovered somewhat unexpected significance of motor neuron positioning for establishing the monosynaptic reflex circuit. We will discuss how this knowledge extends our understanding of motor circuit development and beyond.