Now, eyes are not known for being tough: You can scratch them, jab them, they're soft little orbs. And notably, they're made of organic materials. Not so for the Acanthopleura granulata. This species of chiton has hundreds of tiny eyes dotting the plates that protect it, and the lenses are made of inorganic material. Where eyes are typically made out of protein, chiton eyes are made of a transparent aragonite, which is the same hard, ceramic material that its tough shell is made out of. The lenses, however, were made of larger aragonite crystals than the rest of the armor.