The cerebrospinal fluid (CSF) has long been a 'missing link' in our understanding of brain form, function, and disease. However, recent work has begun to illuminate how the CSF regulates the brain in ways that extend far beyond its passive historical roles and provides unique opportunities for studying, diagnosing, and potentially treating brain disorders. This Keystone Symposia conference brings together an interdisciplinary group of new and established scientists to discuss this newfound excitement about CSF. Talks will feature discoveries about CSF sources (choroid plexus), routes (glymphatics), drainage (lymphatics) and clinical utilities. This conference aims to coalesce an international community that can propel CSF research forward by fostering new ideas, collaborations, and training opportunities. Held jointly with Keystone Symposia’s ‘Brain Therapeutics: Disruptive Technologies and Opportunities for Drug Development,’ the goal of this paring is to stimulate thinking about CSF-based medicinal therapies. CSF has therapeutic advantages over blood because it is 'behind' the blood-brain barrier and equilibrating with the interstitial fluid surrounding brain cells.