A young man, who says he is part of a local criminal gang, poses for a picture holding a gun in the neighbourhood of Korogcho in Nairobi, Kenya, March 19, 2015. Around 2 million people live in the shantytowns packed in around Kenya's capital. Crime is high amid chronic unemployment levels, while basic services and sanitation are scarce. Residents try to make the best of things, eking out a living and picking up work where they can. (Photo by Siegfried Modola/Reuters)

Soldiers pose for a photo during the flower exhibition marking the 105th birth anniversary of the country's founding father, Kim Il Sung in Pyongyang, North Korea April 16, 2017. (Photo by Damir Sagolj/Reuters)

Gold medalists Kikkan Randall and Jessica Diggins of the United States dancing during the medal ceremony for Cross-Country Skiing – Ladies' Team Sprint Free on day 13 of the PyeongChang 2018 Winter Olympic Games at Medal Plaza on February 22, 2018 in Pyeongchang-gun, South Korea. (Photo by Eric Gaillard/Reuters)

These powerful images capture the spear-wielding tribes of Papua new Guinea who believe they are possessed with the spirit of the crocodile. They show how the Kangunaman clansmen scar their backs to resemble reptile scales while the Huli Wigmen wear elaborate headdresses to signal they are ready for battle. (Photo by Trevor Cole/Media Drum World)

Mounted cop in action on Tremont Street in Boston, Massachusetts, 1920 – 1929 (approximate). (Photo by Leslie Jones)

A man uses a floating pitcher to catch a fish after removing it from a net at Keenjhar Lake, near Thatta, February 22, 2015. This technique of fishing using floating pitchers is a unique and traditional one for this community, found only on Keenjhar Lake, one of the largest freshwater lakes in Pakistan, which is famous for its variety of breeding and wintering waterbirds. (Photo by Akhtar Soomro/Reuters)

Young Japanese women dressed in colourful Kimonos take a photo of themselves as they gather for a ceremony marking the “Coming of Age Day” at the Toshimaen Amusement Park in Tokyo, Japan, 11 January 2016. The Coming of Age Day is the day to celebrate young people who turn 20 years old while the age of 20 is considered the beginning of adulthood and is the minimum legal age for voting, drinking and smoking in Japan. (Photo by Kiyoshi Ota/EPA)

A man from the Ogiek community harvests honey in Mount Elgon game reserve, where they have reached an agreement with the government allowing them to remain in their ancestral lands in western Kenya, April 26, 2016. (Photo by Katy Migiro/Reuters)