Measurement of the physical form or structure of one or more nephrons in the kidney. A nephron is made up of a glomerulus, Bowman's capsule, proximal convoluted tubule, loop of Henle, distal convoluted tubule, collecting tubule, and collecting duct. A nephron is the basic functional unit of the kidney and its chief function is to regulate the concentration of water and soluble substances like sodium salts by filtering the blood, reabsorbing what is needed and excreting the rest as urine.