The vagus nerve acts as the highway of the autonomic nervous system, running through the body to every major organ. Researchers have long known that the vagus nerve serves as an information highway, ferrying signals between the brain stem and the rest of the body. Tracing this inner cartography is a challenge—the vagus nerve is made up of some 200,000 nerve fibers. But doing so can unlock new understandings of what the vagus nerve does and how its role changes over time. In a recent study, researchers examined the left and right branches of the vagus nerve in 30 human cadavers in attempt to better map the nerve.