Uric acid is responsible for some of the most common pathological crystallization including gout, the most common arthritis, and uric acid kidney stones. The prevalence of both diseases is constantly rising, and current treatments which mostly focus on reducing the urate levels (gout) or alkalization of urine (kidney stones) are frequently unsuccessful. There is a great need for new treatments to specifically target the crystal nucleation and growth stages. Remarkably, organisms, such as fish and crustaceans, are using uric acid and other purines in their eyes and skin to reflect light. These organisms present exquisite control over crystal morphology and could also delay or entirely prevent crystal formation. We study the mechanism by which these organisms control the organic crystals and identify the key molecular agents which facilitate this control.