A youth dives into a crater filled with water in Aleppo's al-Shaar district, in this July 10, 2014 file photo. (Photo by Hosam Katan/Reuters)

Tommy Lindsey holds an enormous maple leaf that he found in Mount Vernon, Wash., October 28, 2013. Lindsey was walking with his family when he picked up the leaf that is more than two feet from stem to tip and more than 21 inches wide. (Photo by Frank Varga/The Skagit Valley Herald)

Model Ireland Baldwin attends NBC and Time Inc. celebrate the 50th anniversary of the Sports Illustrated Swimsuit Issue at Dolby Theatre on January 14, 2014 in Hollywood, California. (Photo by Dimitrios Kambouris/Getty Images)

The Northern Lights glow green in a spectacular light show above a field of trees frozen solid with snow. (Photo by Jaak Sarv/Solent News & Photo Agency)

Performers line up during the closing ceremony of the 2014 Winter Olympics, Sunday, February 23, 2014, in Sochi, Russia. (Photo by Darron Cummings/AP Photo)

An India Christian devotee reenacts the sufferings of Jesus Christ on the occasion of Good Friday in Mumbai, India, Friday, March 29, 2013. Christians all over the world are marking Good Friday, the day when Christ was crucified. (Photo by Rajanish Kakade/AP Photo)

Coloured X-ray of a barn owl. A physicist has used X-ray to create an extraordinary collection of artwork. Arie van't Riets pictures reveal birds, fish, monkeys and flowers in an incredible new light. The 66-year-old, from Bathmen in the Netherlands, began X-raying flowers as a means to teach radiographers and physicians how the machine worked. But after adding a bit of colour to the pictures, the retired medical physicist realised the potential for an exciting new collection of art. (Photo by Arie van't Riet/Barcroft Media)

Andy Goldfarb, a staff biologist at the Point Defiance Zoo & Aquarium, plays with one of the four clouded leopard cubs currently at the zoo Friday, June 5, 2015 in Tacoma, Wash. The quadruplets were born on May 12, 2015 and now weigh about 1.7 lbs. each. Friday was their first official day on display for public viewing, usually during their every-four-hours bottle-feeding sessions, which were started after the cubs' mother did not show enough interest in continuing to nurse them. (AP Photo/Ted S. Warren)