A team has leveraged its microfluidic Organs-on-Chips technology in combination with a developmentally-inspired hypoxia-mimicking approach to differentiate human pluripotent stem (iPS) cells into brain microvascular endothelial cells (BMVECs). The resulting 'hypoxia-enhanced BBB Chip' recapitulates cellular organization, tight barrier functions and transport abilities of the human BBB; and it allows the transport of drugs and therapeutic antibodies in a way that more closely mimics transport across the BBB in vivo than existing in vitro systems.