" have you ever seen an actual human brain? It’s built in two parts—an outer part called the dura mater and an inner part called the pia mater. These two parts are separated by the arachnoid—a veil of weblike tissue.” Langdon cocked his head in surprise. Gently, she reached up and touched Langdon’s temple. “There’s a reason they call this your temple, Robert. "

― Dan Brown , The Lost Symbol (Robert Langdon, #3)