Alex Plunkett, left, and Sean Hart, both of Arlington, Va., join hundreds participating in the annual International Pillow Fight Day on April 5. Massive pillow fights broke out on the Mall in Washington and in cities around the world. (Photo by Marvin Joseph/The Washington Post)

A spiritual leader (R) of the Huni Kui Indian tribe blows an herbal powder into the nose of a tribal member during a ceremony outside the village of Novo Segredo along the Envira river of Brazil's northwestern Acre state, March 9, 2014. Many indigenous groups, including the Huni Kui, Ashaninka, and Madija, live in villages in the Brazilian rainforest near the border with Peru. (Photo by Lunae Parracho/Reuters)

Smoke billows from Jinnah International Airport in Karachi, Pakistan, June 9, 2014. (Photo by Athar Hussain/Reuters)

Vehicles clog a highway during a hazy day in Beijing, China, Wednesday, February 26, 2014. Beijing remained cloaked in hazardous white pollution hiding much of its skyline Wednesday, despite the announced closures or production cuts at 147 of the city's industrial plants. (Photo by Ng Han Guan/AP Photo)

Photographer Gregg Segal travelled the world to document children and the food they eat in a week. Partly inspired by the increasing problems of childhood obesity, he tracked traditional regional diets as yet unaffected by globalisation, and ironically, found that the healthiest diets were often eaten by the least well off. (Photo by Gregg Segal/The Guardian)

A life-size replica of a Diplodocus dinosaur watches people coming out of the subway in the city center of Bochum, Germany, Monday, August 12, 2019. The exhibition, featuring models of 33 dinosaurs all around the city center, is in Bochum due to the discovery of an 316 million years old dinosaur track found in a stone pit in the city six years ago. (Photo by Martin Meissner/AP Photo)

Men and children gather as a camel is being slaughtered in celebration of Eid al-Adha, in Peshawar, Pakistan on August 12, 2019. (Photo by Fayaz Aziz/Reuters)

A demonstrator runs between burning tires during a curfew, two days after the nationwide anti-government protests turned violent, in Baghdad, Iraq on October 3, 2019. (Photo by Wissm al-Okili/Reuters)