Kidney cortex. Light micrograph of a vertical section through the cortex (outer layer) of a kidney. The cortex tissue (across top) is stained a darker red, and consists mainly of blood vessels going into the filtering units (Bowman's capsules). It is these structures that filter the blood and produce urine. Below these are collecting tubes that go via the loop of Henle (tubes descending downwards into the medulla, lower frame) and convey urine to renal pelvis (not seen). Magnification: x370 when printed at 10 centimetres high.