The eye color is a genetic trait that is determined by the amount and distribution of melanin in the iris. It is a complex process involving several genes towards the final result. Similarly, there are three elements that contribute to iris give your colored : the melanin in the iris epithelium, the melanin in the front of the iris and the density of the iris stroma. In addition to melanin, other pigment acting on the process is the lipochrome. Also, the two types of melanin are involved in the process of eumelanin, the dark brown appearance, and pheomelanin, looking brown-red amarillante. In all eye colors, except for abnormal conditions, the iris pigment epithelium is always eumelanin, performing in large quantity. In this way, the eye color variation is produced in principle by the pigment the front of the iris and how much light is absorbed by the stroma according to their density.