Louveau, the postdoctoral fellow, asked Dr. Kipnis to take a look through the microscope and see what he thought. Kipnis recognized lymph vessels going throughout the meninges, the three membranes that cover the brain and spinal cord: Dura mater, Arachnoid mater, Pia mater. This discovery overturned decades of textbook teaching — the brain is directly connected to the immune system by lymphatic vessels, previously thought not to exist. Prior to late 2015, the belief was that there was no lymphatic system for the brain and central nervous system—there was one, just no one had discovered it! Dr. Kipnis said: “I really did not believe there were structures in the body that we were not aware of… I thought the body was mapped… This changes entirely the way we perceive the neuro-immune interaction . . . We believe that for every neurological disease that has an immune component, these vessels may play a major role.” More tomorrow.