Nature Neuroscience, Published online: 12 February 2026; doi:10.1038/s41593-025-02189-6
The endothelial blood–brain barrier was discovered in the 19th century, and, since then, additional epithelial, glial and meningeal brain barriers have been described. In this issue of Nature Neuroscience, Verhaege and colleagues describe the discovery of an entirely overlooked brain barrier localized at the base of the choroid plexus.