The nephron is the functional unit of the kidney$$ that actually produces urine in the process of removing waste and excess substances from the blood. There are about 1,000,000 nephrons in each human kidney. Each nephron in the mammalian kidney is a long tubule, or extremely fine tube, about 3055 mm (1.22.2 inches) long. At one end this tube is closed, expanded, and folded into a double-walled cuplike structure. This structure, called the renal corpuscular capsule, or Bowman's capsules, encloses a cluster of microscopic blood vessels capillaries called the glomerulus. The capsule and glomerulus together constitute the renal corpuscle. Blood flows into and away from the glomerulus through tiny arteries called arterioles, which reach and leave the glomerulus through the open end of the capsule. In the renal corpuscle, fluid filters out of the blood in the glomerulus through the inner wall of the capsule and into the nephron tubule. As this filtrate passes through the tubule, its composition is altered by the secretion of certain substances into it and by the selective reabsorption of water and other constituents from it. The final product is urine, which is conveyed through the collecting tubules into the renal pelvis.

Kidneys has two layers outer cortex had inner medulla. Each kidney consists of millions of microscopic structural, functional filtering units called "NEPHRON". Each Nephron starts with cup shaped structure called "Bowman's capsules" which continue as 'U' shape convoluted tubule (Henley's loop). Bowman's capsules is associated with the network of thin walled capillaries called "Glamorules". When blood enters into Glamorules with pressure it get filter, the filtrate consist of Glucose, Amino acid, Water, Minerals, Vitamins and metabolic waste like Urea (CH4N2O), Uric acid. When filtrate passes through Convoluted tubule, the surrounding capillaries absorbs essential nutrients living behind Nitrogenous waste, this is called "Selective Reabsorption". The filtrate consists of Nitrogenous waste enters to Urether and Urinary bladder. When Urinary bladder is filled with Urine creates urge to urinate.