Light micrograph of normal human kidney, showing convoluted tubules in the cortex. The tubules are part of the filtration system of the kidney, removing unwanted substances from the blood and discharging them as an aqueous solution, the urine. Each tubule appears outlined in blue with pink nuclei within. The shape of the tubule depends on the plane of section through it. Regions of deep red staining represent sections through blood capillaries which permeate the cortex of the kidney. Magnification: x50 at 35mm size.