Like its namesake, this cave looks out on the real world, as represented by the clouds seen outside it. Instead of seeing a true cave however, the observer perceives but a shadow of the cave’s true nature, cast through the perceptual lenses of both observer and artist. This cave is really the mouth of a tunnel running through the human class I histocompatability protein, one of several molecular fingerprints that identify the cells bearing them as belonging to the body. Invading microbes lack these identification badges and are eliminated by the immune system.