Most people have two kidneys. They lie just underneath the rib cage at the back of the body – one on each side. They are bean-shaped, and about 12.5cm (five inches) long.

Their main job is to make urine. Urine is the water and waste products the body doesn’t need.

The urine leaves the kidneys and goes down two tubes (the ureters) to the bladder. It is stored there until you empty your bladder by going to the toilet.