Are you able to see them? The friend with amazing eyes is walking down the street. You’ve probably met someone with Heterochromia, a rare trait that can cause multicolored or double-blindness. It doesn’t just exist in humans, it also exists in cats and dogs. This is by far one of the most stunning, mysterious, and beautiful physical traits known to mankind.

National Different Colored Eyes Day was created to recognize this beauty and help unravel some of the mysteries surrounding it. Heterochromia can be caused by many factors. Some are genetic traits that are present at birth while others are due to injury or disease. There are three types of heterochromia. Each type is identified by its degree and manifestation.

Heterochromia, which is complete heterochromia, is where each eye has a completely different color than the other. Partial heterochromia is where a part of the eye’s iris is different from the other. This is especially true when it occurs in both eyes.

We have numerous records that it has happened throughout history.

Find out if any of your friends have this trait before you start celebrating. Be subtle, as some people aren’t interested in being made to look ridiculous. Some of the most well-known actors and actresses in the world are also known to be heterochromiacs. You can see the legendary David Bowie, Christopher Walken, Jane Seymore and Mila Kunis. Who would have thought?