Kidneys are paired, bean-shaped organs within the circulatory and urinary systems of vertebrates. Their primary function is to filter blood, removing waste products, excess electrolytes, and regulating the body's fluid volume and acid-base balance. This filtration process occurs through millions of functional units called nephrons, which are responsible for forming urine. The waste products collected include nitrogenous compounds such as urea. Furthermore, the organs play a critical role in maintaining homeostasis by adjusting blood pressure and controlling the concentration of vital substances in the body's plasma.