Our urinary system consists mainly of two bean-shaped glandular organs in the lumbar region of the abdominal cavity, which are called kidneys. They are reddish-brown in colour. Each kidney is approximately 11 centimetres long, 5 centimetres wide and 2.5 centimetres thick. Each of them weighs about 150 grams. Do you know what is the function of the kidney? The main function of the kidneys is to purify our blood by removing the impurities from it. They work as filters. The kidneys also maintain proper proportion of every constituent in the blood. If sometimes the level of sugar, salt or water in blood exceeds the normal level, the kidneys excrete the excess amount from it. They also regulate the formation of urine according to the exigencies of the situation and thus do not allow the blood to become extra thick or thin. The undesirable acids and bases of the blood come out of the body as urine. Each kidney has millions of coiled capillaries. Blood enters the kidney through the renal artery and passes through these capillaries and the dissolved impurities are filtered out. The purified blood returns to the lungs. About 200 litres of blood pass through the kidneys every day. The impurities removed from the blood pass from the kidneys to a bag where they are stored for some time. This bag is known as the bladder. When the bladder is sufficiently filled, one feels the urge to empty it. We pass urine primarily to empty this bladder. Normally, an ordinary person passes 1.5 litres of urine in one day. Any disorder or damage to the kidneys is very dangerous for the body. If the kidneys become defective, impurities in blood go on increasing and have poisonous effect on the body. If somebody‘s kidneys stop functioning, the person dies within a few days. It is, therefore, absolutely essential to have proper treatment of any defect or disease of the kidneys. It is necessary to take proper quantity of food in order to keep them healthy. Excessive eating compels the kidneys to work more to expel more excretory materials and thus the chances of any damage to the kidneys increase. To keep the kidneys healthy, we should take eight to ten glasses of water every day.