U.S Army combat camera photographer Spc. Hilda Clayton took this photo July 2, 2013 that was released by the U.S. Army, that shows an Afghan soldier engulfed in flame as a mortar tube explodes during an Afghan National Army live-fire training exercise in Laghman Province, Afghanistan. The accident killed Clayton and four Afghan National Army soldiers. (Photo by Spc. Hilda Clayton/U.S. Army via AP Photo)

A Maasai man in ceremonial dress poses for visitors to take photographs of him in front of one of around a dozen pyres of ivory, in Nairobi National Park, Kenya Thursday, April 28, 2016. The Kenya Wildlife Service (KWS) has stacked 105 tons of ivory consisting of 16,000 tusks, and 1 ton of rhino horn, from stockpiles around the country, in preparation for it to be torched on Saturday to encourage global efforts to help stop the poaching of elephants and rhinos. (Photo by Ben Curtis/AP Photo)

In a north London hospital, scientists are growing noses, ears and blood vessels in the laboratory in a bold attempt to make body parts using stem cells. It is among several labs around the world, including in the U.S., that are working on the futuristic idea of growing custom-made organs in the lab. (Photo by Matt Dunham/AP Photo)

This 1950s photo provided by the Estate of Vivian Maier and John Maloof Collection shows Maier in a self-portrait as she looks into a storefront wearing a hat in New York. New research about Maier shows the enigmatic Chicago nanny was obsessive about honing her skills as a photographer starting in 1950. (Photo by Vivian Maier/Estate of Vivian Maier and John Maloof Collection via AP Photo)

In this June 17, 2014 photo, a North Korean man takes shelter in the rain next to long propaganda billboards in the town of Samjiyon in North Korea's Ryanggang province. The Associated Press was granted to embark on a weeklong road trip across North Korea to the country’s spiritual summit Mount Paektu. The trip was on North Korea's terms. An AP reporter and photographer couldn't interview ordinary people or wander off course, and government “minders” accompanied them the entire way. (Photo by David Guttenfelder/AP Photo)

This undated photograph shows one of the 14 new species of so-called dancing frogs discovered by a team headed by University of Delhi professor Sathyabhama Das Biju in the jungle mountains of southern India. The study listing the new species brings the number of known Indian dancing frogs to 24 and attempts the first near-complete taxonomic sampling of the single-genus family found exclusively in southern India's lush mountain range called the Western Ghats, which stretches 1,600 kilometers (990 miles) from the west state of Maharashtra down to the country's southern tip. (Photo by Satyabhama Das Biju/AP Photo)

In this Monday, April 27, 2015 photo, a Nepalese man walks over fallen rocks and past a crushed car on the way to Dhunche, Nepal, a village in Langtang National Park, two days after a 7.8-magnatude earthquake hit the region. The photographer, Joe Sieder, said the man was part of a group of Nepalese workers and trekkers who left Syabrubesi earlier that day and hiked about 30 km (19 miles) for 13 hours, mostly over boulder-strewn roads with some small landslides along the way to make their way to a passable road. (Photo by Joe Sieder via AP Photo)