Iris of the eye. Coloured scanning electron micrograph (SEM) of the inner surfaces of the iris and adjoining structures in the human eye. At the top is the cornea, the hole that allows light into the eye. Below this is the iris and ciliary processes (pink). The iris controls the size of the pupil and therefore how much light will enter. The ciliary processes secrete fluids that nourish neighbouring parts of the eye. They are also the sites of attachment for the long, thin zonular fibres (blue) which are responsible for suspending the lens (bottom right). Magnification: x100 when printed 10 centimetres wide