The choroid plexus is a plexus of cells that produces the cerebrospinal fluid in the ventricles of the brain. It consists of a layer of cuboidal epithelial cells surrounding a core of capillaries and loose connective tissue. Choroid plexus participates in brain development, maturation, aging, endocrine regulation, neuroimmune interactions, and pathogenesis of certain neurodegenerative diseases. The choroid plexus consists of a network of capillaries enclosed by a single layer of epithelial cells that together form the blood-CSF barrier. Capillaries in the choroid plexus contain a single layer of endothelial cells interrupted by “pores”; which exhibit a diaphragm between the lumen and the interstitial space. Choroid plexus endothelial cells express high levels of Glut1 glucose transporter; which supports the idea that epithelial and endothelial cells in the choroid plexus provide a metabolic work capability for maintaining ionic gradients and secretory functions across the blood-CSF barrier.