![Microscopy image of the highly convoluted choroid plexus epithelium in organoids expressing tight junction markers and membrane transporters that regulate entry of molecules into the brain](https://www2.mrc-lmb.cam.ac.uk/wordpress/wp-content/uploads/Lancaster_IoR_6-20-150x150.jpeg)
The human brain is bathed in a supportive fluid called the cerebrospinal fluid (CSF) that provides various nutrients. Madeline Lancaster’s group have now developed a new brain organoid that produces CSF and has the potential to predict whether drugs can access the brain.