A secret recipe for colorful and versatile animal crystals

What do fish, chameleons, crabs and Walter White, the chemistry teacher from "Breaking Bad," all have in common? The answer is that they all know how to make crystals. But, unlike the incorrigible White, who manufactured mind-altering methamphetamine crystals for criminal ends, the others make natural crystals for far more wholesome purposes: from vision and camouflage to regulating heat and communicating.