The organ that produces urine is the kidney. The kidneys are part of the urinary system and are one of the body’s primary secretory organs, often producing urine to help the body eliminate metabolic waste and excess water. The kidneys generally function through renal units, which are composed of tubules and glomeruli. Small molecules in the plasma and water are usually filtered as the blood flows through the glomerular capillaries to form the primary urine; solutes and water in the primary urine are reabsorbed at the tubules and collecting ducts to form the final urine which is then excreted from the body. While producing urine and maintaining electrolyte and fluid balance, the kidneys also have endocrine functions, which can help the body regulate blood pressure and play an important role in maintaining human health. Therefore, it is recommended to have regular medical checkups to see if your kidneys are functioning normally. If you experience reddish or foamy urine, you should pay attention to it and go to the hospital immediately for examination and treatment.