Some of London's telephone operators and engineers, trying out their gas masks at the anti-gas civilian training centre in Gloucester, where they were taught how to deal with gas attacks. (Photo by Harry Todd/Fox Photos/Getty Images). 13th February 1937

Two styles of cleaned bird's nest, Yan Zhan (L) and Su Zhan (R) await repacking at a processing plant in Kuala Lumpur, February 17, 2015. Prized in China for is alleged health benefits for hundreds of years, nests made from swiftlets' saliva are being mixed into coffee and cereal as the Southeast Asian producers of the delicacy seek to broaden its appeal, and their profit margins. The nests are among the world's most expensive foods, selling for up to $2,500 a kg and the swiftlets that weave them are indigenous to Indonesia, Malaysia, Thailand and Vietnam. (Photo by Olivia Harris/Reuters)

Two baby orangutans play with each other at the wildlife department in Kuala Lumpur, Malayasia, October 19, 2015. The Malaysian wildlife department in July seized two baby Sumatran orangutans, found in duffel bags, from traffickers who were attempting to sell them to buyers in Malaysia. According to local media, the orangutans will be returned to Medan, Indonesia on Tuesday. The illegal wildlife trade is estimated to be $8 billion a year worldwide, according to TRAFFIC, a wildlife trade monitoring network. (Photo by Olivia Harris/Reuters)

Victoria's Secret angels Adriana Lima, Candice Swanepoel, Alessandra Ambrosio and Miranda Kerr arrive at the 2011 Victoria's Secret SWIM Collection Pink Carpet Event hosted by VS Angels at Club L on March 30, 2011 in Los Angeles, California. (Photo by Jerod Harris/Getty Images for Victoria's Secret)

Dameon Harris of Nevada gets used to the controls of a bulldozer at Dig This October 27, 2011 in Las Vegas, Nevada. At Dig This, tourists take a short class and can then operate full-size hydraulic excavators and track-type bulldozers in a giant sandbox while being guided by instructors over headsets. (Photo by Ethan Miller/Getty Images)

Flamingo chicks walk in an enclosure before they are tagged in Fuente de Piedra, Spain, on Jule 19, 2014. Fuente de Piedra lagoon is a natural reserve with more than 170 different species recorded and one of the main breeding grounds for flamingos in the Iberian Peninsule. Hundreds of flamingo chicks are tagged and checked annually to record the evolution of the species. (Photo by Pablo Blazquez Dominguez/Getty Images)

A journalist operate a harness with multiple recording devices capable of recording and live streaming outside the Great Hall of the People where the opening session of the Chinese People's Political Consultative Conference (CPPCC) was held in Beijing, China, Friday, March 3, 2017. Thousands of delegates have gathered at the Chinese capital for the opening of the annual session of the Chinese People's Political Consultative Conference, which advises the rubberstamp parliament, whose annual session begins Sunday. (Photo by Ng Han Guan/AP Photo)