Neuroscientist Laura Lewis and colleagues at MIT have visualized, using real-time imaging, pulsatile cerebrospinal fluid flow in the brain’s glymphatic system that clears toxic waste products such as amyloid beta and tau. The newly discovered perivascular pathways facilitate efficient removal of neurotoxic substances implicated in neurodegenerative diseases. These findings provide crucial insight into how sleep and fluid dynamics maintain neural health, challenging prior assumptions about waste clearance limited by the blood–brain barrier. This work opens therapeutic possibilities for combating Alzheimer’s and related disorders by targeting cerebrospinal fluid circulation mechanisms.