In this timed-exposure night photo taken early on February 12, 2017, Mount Sinabung volcano spews reddish smoke and ash, as seen from the Karo district in North Sumatra province. Activity levels have increased in the past week, with Sinabung shooting hot ash clouds into the sky dozens of times, according to the local volcano monitoring agency. (Photo by AFP Photo/Stringer)

Baka pygmies in their forest home preparing food in, Sangha Forest, Central African Republic, February 2016. Here, in their forest home, traditional life continues in the face of multiplying challenges ranging from poachers, to ill health. Deep in the rainforests of central Africa lives one of the world’s most mysterious tribes. (Photo by Susan Schulman/Barcroft Images)

A reveller holds her dog dressed in costume, during the Rio Dog Carnival, known as the Blocao – with “bloco” meaning street party and “cao” dog, during pre- carnival celebrations at Copacabana beach in Rio de Janeiro, Brazil, on February 19, 2017. (Photo by Yasuyoshi Chiba/AFP Photo)

Heidi Klum attends the Heidi Klum's 16th Annual Halloween Party sponsored by GSN's Hellevator And SVEDKA Vodka At LAVO New York on October 31, 2015 in New York City. (Photo by Mike Coppola/Getty Images for Heidi Klum)

A giant storm cloud can be seen in the sky above swimmers near Mollymook Beach, south of Sydney, March 5, 2014. (Photo by David Gray/Reuters)

A driverless vehicle runs at Vanke's Building Research Centre testing area in Dongguan, south China's Guangdong province November 2, 2015. The country's largest property developer, China Vanke, is investing in its own robots to do certain jobs in the face of a labor shortage in the world's most populated country. This driverless car is among the robots that Vanke is aiming to bring in. (Photo by Tyrone Siu/Reuters)

A mother prays for success for her child in the college entrance examinations at a Buddhist temple in Seoul, South Korea, November 12, 2015. About 630,000 students on Thursday sat for the annual exams that could lead them to one of the country's top universities. In South Korea, there is no higher achievement than to be accepted by a prestigious university. As a result, many students prepare for these entrance exams from an early age, often studying up to 16 hours a day for years to take this test. (Photo by Kim Hong-Ji/Reuters)

Miners search for jade stones at a mine dump at a Hpakant jade mine in Kachin state, Myanmar November 25, 2015. (Photo by Soe Zeya Tun/Reuters)