The iris is the colorful part of the eye and is as individual as a fingerprint. The so-called iris or "colorful aperture" of the eye can appear in many shades of gray, green, blue or brown due to an individual pigment distribution.

Regardless of its color, the iris regulates the amount of light entering the eye through two muscles. It can either constrict or dilate depending on the light conditions. It functions like the iris of a camera: It regulates the incident light that falls into the pupil - the aperture of the eye.

90 percent of all people worldwide have brown eyes. Next to gray and blue, green is the rarest eye color with only 2 percent. The color of the iris is genetically determined: the predisposition for brown eyes is most dominant. Thus, most people have brown eyes, even though babies are often born with blue eyes.