Another peek down the microscope

This is a photograph of a very thin slice of kidney, stained to show the structure of the organ.
The large roundish structure at the centre is a glomerulus, a complex of blood capillaries sitting in a space in a thin walled sac (stained blue) known as a Bowman's capsule. (Bowman's capsules are  named after the English surgeon Sir William Bowman who identified them in 1842). This is where where the blood is filtered, the first stage in the production of urine. The other structures are sections through the Convoluted Tubules which are responsible for adjusting the composition and concentration of the urine.