“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)

(L-R) Ozzy Osbourne and son, producer Jack Osbourne visit the Tribeca Film Festival 2011 portrait studio on April 25, 2011 in New York City. (Photo by Larry Busacca/Getty Images for Tribeca Film Festival)

A masked reveller parades through the streets on the first day of the carnival season in Lucerne, Switzerland, 12 February 2015. In the background the well known Kappellbruecke bridge. (Photo by Alexandra Wey/EPA)

A Saudi soldier fires a mortar towards Houthi movement position, at the Saudi border with Yemen April 21, 2015. (Photo by Reuters/Stringer)

People cross the street in central Pyongyang, North Korea May 4, 2016. (Photo by Damir Sagolj/Reuters)

A supercell that spawned a tornado earlier makes it was east north of McLean, Texas on April 16, 2015 in Texas, United States. Huge hail, terrifying lighting and giant supercells the size of buildings – these incredible images depict a year in the life of a storm chaser. Shot in 2015 by photographer Mike Olbinski, 40, this series of pictures show both the beautiful and the extreme nature of weather in the United States. (Photo by Mike Olbinski/Barcroft Media)

Residents watch the forest burn in Portezuelo, Chile, Sunday, January 29, 2017. Chilean President Michelle Bachelet has announced that the country will continue with its various measures to deal with wild fires, one of the biggest natural disasters in the country for decades, according to a government report released on Sunday. (Photo by Esteban Felix/AP Photo)

Members of the Palestinian Hamas security forces show their skills as they take part in a graduation ceremony in Gaza City on January 22, 2017. (Photo by Mahmud Hams/AFP Photo)