Cerebrospinal fluid

Cerebrospinal fluid or cerebral spinal fluid or CSF is a clear, colorless liquid that fills the hollow spaces (ventricles) surrounding the brain and the spinal cord, as well as between two of the meninges.

Function
Cerebrospinal fluid provides a mechanical barrier that cushions against shock. CSF is made by tissue called the choroid plexus in the ventricles in the brain.