Master Regulator Sympathetic neurons and the adrenal medulla are part of the autonomic nervous system, which is important in the control of a variety of bodily functions and in responses to stress. Interactions between the nervous system and the vascular system have been poorly explored. During development, sympathetic neurons and adrenal medulla cells are derived from the same precursors—neural crest cells—embryonic cohorts that undergo massive migration in the body. Using blood vessel–specific gene manipulation in chicken embryos, Saito et al. (p. 1578 ) revealed a role for the dorsal aorta in regulating the early migration of neural crest cells and later in development on the segregation of adrenal medulla and sympathetic neurons. The dorsal aorta expresses multiple soluble morphogenetic and growth factors that regulate complex morphogenesis in a spatiotemporal manner. Furthermore, in mice, the morphogenesis of the adrenal medulla was controlled both by the aorta and the adrenal cortex.