Kidney filtering units. Light micrograph of a section through a human kidney, showing the blood supply (red) to the filtering units, the malpighian corpuscles. The round clumps (red) are glomeruli, tightly coiled balls of blood vessels where blood filtering takes place in the kidneys, removing waste products like urea from the blood. The blood vessels have been injected with a contrast medium so that they can be seen here. This tissue is from a childs kidney.
