Subarachnoid space:

close-up view of the meninges showing the subarachnoid space.

close-up view of the meninges showing the subarachnoid space.

space between the arachnoid and pia mater, which is filled with cerebrospinal fluid.

Read more: Know your brain - Meninges

Watch this 2-Minute Neuroscience video to learn more about the meninges.