A hand of a labourer pushes bricks at a traditional brick factory in Arab Mesad district of Helwan, northeast of Cairo, May 14, 2015. About 45 labourers are employed at the brick factory and most work 10 hours a day. Adult workers earn a daily wage of 70 Egyptian pounds ($9) and child workers earn 40 Egyptian pounds ($5). The labourers, who are usually temporary or seasonally employed in Egypt's brick-making industry, experience unsafe work conditions, according to local media. (Photo by Amr Abdallah Dalsh/Reuters)

A Naga sadhu, or naked Hindu holy man, pauses inside a tent during Kumbh Mela, or Pitcher festival, at Trimbakeshwar, India, Thursday, August 27, 2015. Hindus believe taking a dip in the waters of a holy river during the festival will cleanse them of their sins. The festival is held four times every 12 years. (Photo by Bernat Armangue/AP Photo)

At the beginning of the 20th century, Edward S. Curtis set out to document what he saw as a disappearing race: the Native American. From 1907 to 1930, Curtis took more than 2,000 photos of 80 tribes stretching from the Great Plains to the Pacific Northwest and Alaska. He then published and sold these photos, along with narrative text, in 20 volumes of work known as “The North American Indian”. It is one of the most significant collections of its kind, “probably the most important photographic document of its age and its topic,” said Jeffrey Garrett, associate university librarian for Special Libraries at Northwestern University. (Photo by Edward S. Curtis)

Jan Kara (R) and Jan Holan pedal their boat, made with plastic bottles, on the Elbe river near Kostelec nad Labem July 15, 2014. Jan Kara, a 22-year-old student, and Jakub Bures, a 22-year-old car mechanic, built the 10-metre (32.8-feet) long boat from 5000 plastic bottles strapped to a wooden frame. (Photo by David W. Cerny/Reuters)

Super-cell thunderstorms, whirling tornados and lightning bolts illuminating the sky – these photos capture the terrifying brilliance of American storms. (Photo by Brandon Goforth/Solent News & Photo Agency)

Actress Tang Wei poses at the “Wu Xia” portrait session during the 64th Annual Cannes Film Festival on May 15, 2011 in Cannes, France. (Photo by Andreas Rentz/Getty Images)

A man runs away during a police round up of suspected drug addicts in Kabul, Afghanistan December 27, 2015. Afghan officials have opened a new drug treatment centre in an abandoned NATO military base in Kabul, in the latest attempt to stamp out the country's massive problem of drug abuse. Camp Phoenix, a former training camp on the edges of Kabul set up by the U.S. army in 2003, will take in around 1,000 homeless drug addicts who will receive food, medical attention and treatment, said Public Health Minister Ferozuddin Feroz. (Photo by Ahmad Masood/Reuters)

People carry lychee for sale on a motorbike on a street in Luc Ngan, Bac Giang province, Vietnam, 22 June 2016. Lychee output in Bac Giang province is expected to reach 130,000 tonnes this year. China is still Vietnam's main lychee export market so far, buying around 60 percent of the annual crop, according to official reports. (Photo by Luong Thai Linh/EPA)