Urine is liquid biological waste excreted by the kidneys. The human body produces urine, as do all mammals, reptiles, birds, fish, and amphibians. Urine is mostly water, and also contains urea, creatinine, waste enzymes and hormones, proteins, carbohydrates and fatty acids. Urine also contains large numbers of bacteria, so coming into contact with or ingesting it is unhygienic and can be harmful.
Urine has been used since ancient times for bleaching cloth and even for brushing teeth. Roman emperor Vespasian levied a tax on stale urine, obtained from street latrines and urns placed for the purpose of collection, and stored for several days, which allowed bacteria to development abundant ammonia content, commonly used for bleaching cloth.
Sociologically, urine's smell and the potential harm it can cause in terms of infection make it taboo in many cultures. Urinating on objects is sometimes done in order to show extreme disapproval, or to humiliate, although such behavior has no place in civilized society. In James Clavell's novel Shõgun the Portuguese ship's captain Blackthorn is punished for insulting his Japanese captor, by literally doing to Blackthorn what Blackthorn had figuratively said to him, as a "lesson".