“In anatomy, heterochromia refers to a difference in coloration, usually of the iris (but also of hair or skin). Although infrequently seen in humans, complete heterochromia is more frequently observed in other species, where it almost always involves one blue eye”. – Wikipedia (Photo by StooMathiesen)

An Andean man and a woman, depicting Inca's legendary characters Manco Capac and Mama Ocllo, pose for a portrait in a Uros island at Lake Titicaca before a re-enactment in Puno November 5, 2014. The Uros islands are a group of 70 man-made totora reed islands floating on the lake, which according to Peru's tourism board iPeru is the world's highest navigable lake at over 4,000 meters above sea level. The Uros people fish and hunt, but tourism is their main source of livelihood. (Photo by Enrique Castro-Mendivil/Reuters)

A Burmese worker sets up Christmas lights inside a woman's clothing store inside a shopping mall December 6, 2011 in Nay Pyi Taw, Myanmar. (Photo by Paula Bronstein/Getty Images)

Imagine living in the sea where it is permanently dark, cold, and food is hard to find. For many animals at depth, it may be weeks to months between meals. If you find something to eat, you have to hang on to it. This is why so many deep-sea fishes have lots of big teeth. This dragonfish, spotted off the coast of Australia, even has teeth on its tongue. They would be terrifying animals ... if they weren’t the size of a banana. (Photo by Julian Finn/Museum Victoria)

A dog wears fake eyes while riding a motorcycle in Samut Sakhon, Thailand June 23, 2016. (Photo by Jorge Silva/Reuters)

People take a selfie at the abandoned former Soviet R12 nuclear missile launch site in Zeltini, Latvia, July 22, 2016. Hidden in the forests of Aluksne, near Latvia's north-eastern border with Russia, the remains of a former Soviet nuclear missile base are a magnet for tourists now rather than a top-secret site manned by soldiers. (Photo by Ints Kalnins/Reuters)

A youth stands near a cow and a sheep that were sacrified in the village of Miratovc for the celebration of Eid-al-Adha, near the town of Presevo, southern Serbia September 24, 2015. Muslims across the world celebrate the annual festival of Eid al-Adha or the Feast of the Sacrifice. (Photo by Hazir Reka/Reuters)

A reveller takes part in an annual block party known as “Cordao de Prata Preta”, one of the many carnival parties to take place in the neighbourhoods of Rio de Janeiro, February 6, 2016. (Photo by Pilar Olivares/Reuters)