Abstract: The heart contains its own nervous system—a small but essential network of neurons known as the intrinsic cardiac nervous system. Distinct neuronal populations within this “little brain” perform specialized roles: some mediate parasympathetic control of heart rate and coronary blood flow under baseline conditions, whereas others maintain electrical stability and protect against cardiac arrest during intense physiological or psychological stress. This functional specialization emerges through a precisely coordinated developmental process. Intrinsic cardiac neurons arise primarily from Schwann cell precursors that migrate along the vagus nerve and enter the developing heart at defined locations. Their migratory paths establish the initial spatial framework, while signals from the cardiac environment direct neuronal differentiation, molecular identity, and organization into stereotyped ganglia. Extracellular matrix interactions are particularly important for supporting neurogenesis and stabilizing this architecture. Together, these findings reveal how the heart helps build a specialized neural network that maintains cardiovascular function and protects the heart during stress.