“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)

A Tufted Capuchin sits in a hanging food tray on a tree in it's enclosure at Sydney Zoo on February 24, 2020 in Sydney, Australia. Sydney Zoo, located at Bungarribee Park in Western Sydney, is the first new zoo to be built in Sydney in more than 100 years. The Zoo opened to the public on 7 December 2019. (Photo by Mark Kolbe/Getty Images)

People take pictures of the sun rising next to the buildings of the banking district in Frankfurt, Germany, Saturday, December 28, 2019. (Photo by Michael Probst/AP Photo)

These images give a rare insight into the life of a 19th Century Indian Maharajah. Maharajah Ram Singh ruled in the famous pink city of Jaipur between 1835 and 1880, and was also a keen photographer. Here: Full portrait of a woman in the harem in the royal palace of Jaipur, India, 1857 – 1865. (Photo by Maharaja Ram Singh III/Alinari via Getty Images)

For centuries the Highlands peoples of Papua New Guinea fought over land, women and pigs. Sorcery and battle skills could elevate a clan to Bigmanship, where the bigger the “presentation”, the bigger the man. Clans therefore would paint their bodies and create fearsome masks as part of their psy. Here: These are the terrifying tribe of “mudmen” from a remote part of Papua New Guinea. (Photo by Jeremy Hunter/Exclusivepix Media)

In this August 31, 2017, photo, mock fish are displayed to offer to the ancestors during the “Hungry Ghost Festival” in Hong Kong. Countless hungry and restless ghosts are roaming Hong Kong, and the world, to visit their living ancestors, at least according to Chinese convention. In traditional Chinese belief, the seventh month of the lunar year is reserved for the Hungry Ghost festival, or Yu Lan, a raucous celebration marked by feasts and music. (Photo by Kin Cheung/AP Photo)

A tourist has her photo taken wearing a Santa hat on Christmas Day on Bondi Beach in Sydney, Australia on December 25, 2018. (Photo by Peter Parks/AFP Photo)