There are three layers of membranes that lie between the skull and the brain matter itself: the dura mater, which is thick, white, and tough, the arachnoid mater, which is cushiony and resembles spider webs, and the pia mater, with is a thin, clingy, delicate envelope that surrounds the brain and spinal cord. Collectively, all three membranes are known as the meninges. (Some people think the words should be "matter", but it's actually "mater", from the Latin word for "mother".)