What is the basic structural and functional unit of the kidney called?

Each kidney is composed of about 1 million nephrons, which are the basic structural and functional units that filter blood and form urine. The kidneys work to eliminate the byproducts of cellular metabolism from blood plasma. These metabolic byproducts (waste products) include: uric acid, creatinine, urea, and excess sodium, potassium, and chloride. The kidney must also retain and recycle important components of blood plasma that the body needs like water, electrolytes, and protein.