If you've ever had a trickster tell you that your epidermis is showing, have no fear. Your pal is just being clever by telling you the top layer of your skin is visible. It would be pretty hard to hide all of your skin; after all, skin is the largest organ in the human body, at 22 square feet (2 square meters). Since your skin is bound to show sometime, you should know how to care for it. Test your knowledge on that very subject in this skin-tingling quiz.