Nephrons are the functional units of the kidney. They are microscopic tubules that are responsible for the filtration, reabsorption, and secretion of water and other various substances. Each kidney contains around one million nephrons, and each nephron is composed of a glomerulus and a renal tubule. The glomerulus is a cluster of capillaries that filter the blood, while the renal tubule is responsible for the reabsorption, secretion, and excretion of needed and unwanted substances. The nephron is responsible for the regulation of the body’s water balance, electrolyte levels, and acid-base balance.