Urea, also known as carbamide, is the diamide of carbonic acid with the chemical formula (NH₂)₂CO. It is a nitrogen-containing substance produced by some living organisms as a means of eliminating ammonia, which is highly toxic to them. In animals, it is found in the blood, urine, bile, and sweat. Urea appears as a white crystalline solid, either spherical or granular in shape. It is hygroscopic, meaning it can absorb water from the atmosphere, and has a slight ammonia odor. Commercially, urea is available in pellets, granules, or dissolved, depending on its intended application.