Two chimpanzees share a piece of watermelon at Taronga Zoo on December 23, 2010 in Sydney, Australia. (Photo by Rick Stevens/Taronga Zoo via Getty Images)

“Contrails (short for “condensation trails”) or vapour trails are artificial clouds that are the visible trails of condensed water vapour made by the exhaust of aircraft engines. As the hot exhaust gases cool in the surrounding air they may precipitate a cloud of microscopic water droplets or, if the air is cold enough, tiny ice crystals”. – Wikipedia

Photo: An airplane leaves a vapor trail as it flies in front of he moon on January 17, 2007 above Hanover, Germany. (Photo by Alexander Hassenstein/Getty Images)

In this November 28, 1966 file photo, one of the 10 beagles involved in the first test of the Veterans Administration Hospital in East Orange, N.J. smokes a cigarette through a machine linked to its windpipe by a plastic tube to test any link between smoking and emphysema. (Photo by AP Photo)

Russian pop art photographer Sergey Chilikov captures a nation liberated from the social oppression of late-era Soviet rule – at parties, in the streets, and bouncing high. His exhibition, Photoprovocations, will be at Photo London, 19-22 May. Here: Yoshkar-Ola, Matrosova Street (1995). (Photo by Sergey Chilikov)

This photo series shows curvy canines and flexible felines participating in a spot of yoga. The shots feature the animals in the likes of the lotus position, balancing on two legs, and stretching in ways that would make the greatest of yoga masters proud. Photographer Dan Borris came up with the idea for the series in 2000, when he was asked by a friend to photograph her in a yoga pose while her dog bothered her. Pictured: Wally. (Photo by Dan Borris/Caters News)

Roland Miller is on a mission to document the deserted sites of America’s space race. He has photographed launch pads, bunkhouses and research facilities across the country, some of which no longer exist or are closed to the public on secure military bases. His book, “Abandoned in Place”, is published by the University of New Mexico Press in March. Here: Launch Pad and Gantry with Hermes A-1 Rocket – V2 Launch Complex 33, White Sands missile range, New Mexico in 2006. (Photo by Roland Miller)

A boat sails behind a woman looking through binoculars as she sits on a cliff on a sunny day in Sydney, Australia, May 29, 2016. (Photo by David Gray/Reuters)

Some of the most powerful narratives of the past decade have been produced by a forward-thinking generation of women photojournalists as different as the places and the subjects they have covered. National Geographic's “Women of Vision” exhibit features the work of 11 photographers and is on display at the Fernbank Museum of Natural History in Atlanta until January 3, 2016. Here: Nujood Ali stunned the world in 2008 by obtaining a divorce at age 10 in Yemen, striking a blow against forced marriage. (Photo by Stephanie Sinclair/National Geographic)