reviews the blood-brain barrier (BBB), the barrier that separates the circulation system from the brain"s interstitial fluid, as well as the blood-CSF barrier (BCB), which is the one that separates the blood and cerebrospinal fluid; addresses the evidence that suggests that the brain barriers may play an important role in neuroscience research; provides a general review of gross anatomy, microstructure, and physiology of BBB and BCB; emphasizes the in vivo, as well as the in vitro, techniques; overs mathematical approaches and theoretical concerns.