Light micrograph of a section through the inner medulla of a kidney. The function of the kidney is to filter waste products from the blood. Filtering units in the outer cortex of the kidney filter the waste products and pass them through tubules to loops of Henle in the medulla (purple tubes). From here it passes into collecting ducts that transport it to the bladder as urine. Magnification: x50 when printed at 15cm wide.