When someone asks, "What color are your eyes?" he should really be asking "What color are your irises?" because it is the iris that contains the pigment that determines the color of your eyes. Despite the fascination eye color holds for us, the genes responsible for it in humans are not well-known and are more complex than most people think.

Iris Structure

The iris is the most visible portion of the uveal tract, which is the middle compartment of the eye. The iris is made up of blood vessels and connective tissue, in addition to melanocytes and other pigmented cells that are responsible for its distinctive color.

The iris contains muscles that control its movement and allow for changes in the size of the pupil, controlling the amount of light that enters the eye and that ultimately reaches the retina. Though its function is easily observed...