Why are all babies born with blue eyes?

You inherit your eye color from your parents, but no matter what the color is now, it may have been blue when you were born. Why? Melanin, the brown pigment molecule that colors your skin, hair, and eyes, hadn't been fully deposited in the irises of your eyes or darkened by exposure to ultraviolet light. The iris is the colored part of the eye that controls the amount of light that is allowed to enter. Some other animals are born with blue eyes, too, such as kittens.

Melanin is a protein. Like other proteins, the amount and type you get is coded in your genes. Irises containing a large amount of melanin appear black or brown. Less melanin produces green, gray, or light brown eyes. If your eyes contain very small amounts of melanin, they will appear blue or light gray. People with albinism have no melanin in their irises and their eyes may appear pink because the blood vessels in the back of their eyes reflect light.

Melanin production generally increases during the first year of a baby's life, leading to a deepening of eye color. The color is often stable by about 6 months of age. However, several factors can affect eye color, including use of certain medications and environmental factors. Some people experience changes in eye color over the course of their lives. People can have eyes of two colors. Even the genetics of eye color inheritance isn't as cut-and-dried as was once thought, as blue-eyed parents have been known (rarely) to have a brown-eyed child!