Syrian refugees sit behind barbed wire as they wait to cross into Macedonia at the Greek-Macedonian border, near the village of Idomeni, August 21, 2015. (Photo by Yannis Behrakis/Reuters)

People walk through crop circles in a cornfield near Raisting, Germany, on July 28, 2014. According to media reports, a balloonist had discovered the circle some days ago. Since then, hundreds of people came to the field to watch it, however it is unclear who did create the pattern. (Photo by Karl-Josef Hildenbrand/DPA)

An officer of the Afghan border police throws an assault rifle to a policeman participating in a military exercise on the outskirts of Herat, Afghanistan, Monday, September 7, 2015. Twelve female and seventy male border police personnel participated in the military exercise near the border with Iran in Herat province. (Photo by Hoshang Hashimi/AP Photo)

Men transport a sheep on their motorcycle after buying it at an old cattle market named “Al Emam Market” ahead of the Muslim festival Eid al-Adha in Cairo, Egypt, September 19, 2015. Muslims across the world are preparing to celebrate the annual festival of Eid al-Adha or the Festival of Sacrifice, which marks the end of the annual hajj pilgrimage, by slaughtering goats, sheep, cows and camels in commemoration of the Prophet Abraham's readiness to sacrifice his son to show obedience to Allah. (Photo by Amr Abdallah Dalsh/Reuters)

“Thunderstruck”. Summer stom. A super cell formed off the coast of New Zealand, intensified and swept across Christchurch and North Canterbury, February 23, 2014. Photo location: Christchurch, New Zealand. (Photo and caption by David Hardy/National Geographic Photo Contest)

Models walk the runway during the Maison Margiela Spring Summer 2016 show as part of Paris Fashion Week on January 27, 2016 in Paris, France. (Photo by Francois Durand/Getty Images)

A six-year-old acrobat performs on the opening of a tourist festival in Bozhou, Anhui province, China May 3, 2015. (Photo by Reuters/China Daily)

Boys walk home for lunch from school in the village of Kogelo, west of Kenya's capital Nairobi, July 16, 2015. U.S. President Barack Obama visits Kenya and Ethiopia later this month. His ancestral home of Kogelo is home to Sarah Hussein Obama, his step-grandmother. The Kenyan village, burial place of Obama's father, features an open-pit goldmine, a pork butcher's, a school named after their most famous son and outdoor market stalls. Villagers get around by motorbike taxi or on foot while a donkey-cart transports water. Children, some of them named Obama in honour of the President, walk to and from school together. (Photo by Thomas Mukoya/Reuters)