While almost every living organism possesses an excretory system, most reptiles don’t eliminate excess nitrogen-containing waste in the form of liquid urine. Reptiles don’t urinate like humans do; instead, they pass these solid “urates” (left). Researchers found that urates consist of tiny microspheres composed primarily of uric acid (right). X-ray analysis also revealed that these spheres contain even smaller nanocrystals composed of uric acid and water. They found that these small amounts of uric acid may help convert the reptiles’ accumulated ammonia into a less toxic, excretable solid form.