Manman Luk, a freelance model and make up artist, poses inside her 100-square-foot (9-square-metre) sub-divided unit, paying a monthly rent of HK4,700 ($606) in Hong Kong, China January 6, 2017. (Photo by Bobby Yip/Reuters)

The sky looked on fire this morning, as it made the clouds glow red, just before sunrise at Peterborough Rowing Lake, in Nene Park, UK on January 18, 2017. (Photo by Paul Marriott/Rex Features/Shutterstock)

Paramasivan points to the statue of sun god Surya at a temple outside the Kodaikanal Solar Observatory, India, February 5, 2017. In the early morning darkness, Devendran P. walks up a hill to a solar observatory in India's southern hill town of Kodaikanal, trudging the same path his father and grandfather walked in a century-old family tradition of studying the sun. (Photo by Danish Siddiqui/Reuters)

Planned improvements to Rio’s favelas have meant increases in rent, forcing the poorest families into squatting in unoccupied buildings. Photographer Tariq Zaidi visits the Mangueira community favela, less than 1km from the showpiece Maracanã stadium, to see what life is like for the women living there. Here: Victoria, 12, at her home in Mangueira. (Photo by Tariq Zaidi/The Guardian)

The fourth annual BigPicture Natural World Photography Competition aims to celebrate the diversity of life on Earth, and encourages people to protect and conserve it. Here: “The Salmon Catchers”. Terrestrial Wildlife. To capture this view of a mother grizzly bear and her cub, photographer Peter Mather set up a camera trap on a log that he knew the bears tended to traverse while fishing for salmon, in the Yukon River watershed in Canada. (Photo by Peter Mather/BigPicture Natural World Photography Competition 2017)

A Southwest Airlines jet takes off from Reagan National Airport with a thunderhead to the east on June 20, 2017 in Alexandria, VA. (Photo by Jonathan Newton/The Washington Post)

Smoke plumes rise from Mount Etna, one of the most active volcanoes in the world in Sicily, Italy on June 28, 2016. (Photo by Etna Walk/Rex Feature/Shutterstock)

In this Tuesday, June 23, 2015, photo, an Israeli vendor waits for clients at the southern Israeli town of Sderot, next to the Israel-Gaza border. A year after the Gaza war, the community in southern Israel, long battered by rockets from the Hamas-run territory next door, has slowly recovered and is even seeing a quiet boom. (Photo by Oded Balilty/AP Photo)