AbstractThe polyvagal theory has led to the understanding of the functions of the autonomic nervous system in biological development in humans, since the vagal system, a key structure within the polyvagal theory, plays a significant role in addressing challenges of the mother–child dyad. This article aims to summarize the neurobiological aspects of the polyvagal theory, highlighting some of its strengths and limitations through the lens of new evidence emerging in several research fields—including comparative anatomy, embryology, epigenetics, psychology, and neuroscience—in the 25 years since the theory's inception. Rereading and incorporating the polyvagal idea in light of modern scientific findings helps to interpret the role of the vagus nerve through the temporal dimension (beginning with intrauterine life) and spatial dimension (due to the numerous connections of the vagus with various structures and systems) in the achievement and maintenance of biopsychosocial well‐being, from the uterus to adulthood.