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

Spectators are swept by huge waves while watching tides of Qiantang River at a dike on August 31, 2011 in Haining, Zhejiang Province of China. More than 20 spectators were injured by strong tides as the typhoon Nanmadol approached on Wednesday. (Photo by ChinaFotoPress/Getty Images)

Martin Garwood prepares to release baby penguins at Sydney Aquarium on January 18, 2012 in Sydney, Australia. Three baby penguins were released into the aquarium and reunited with their parents for the first time since birth. (Photo by Lisa Maree Williams/Getty Images)

A high temperature alerts were issued as a record-setting summer heat wave continued to bake most parts of south China. (Reuters)

Photographers April Maciborka and David Wile teamed up to create their recent series Pucker. In each instance babies were handed their very first lemon and encouraged to take a bite. Just looking at their images will make your lips twitch.

Andy Goldfarb, a staff biologist at the Point Defiance Zoo & Aquarium, plays with one of the four clouded leopard cubs currently at the zoo Friday, June 5, 2015 in Tacoma, Wash. The quadruplets were born on May 12, 2015 and now weigh about 1.7 lbs. each. Friday was their first official day on display for public viewing, usually during their every-four-hours bottle-feeding sessions, which were started after the cubs' mother did not show enough interest in continuing to nurse them. (AP Photo/Ted S. Warren)

Indonesian rescuers search for victims of the crashed military airplane in Medan, North Sumatra, Indonesia, 30 June 2015. At least people 49 people were killed after an Indonesian military plane crashed in North Sumatra and burst into flames, officials said. Air Force chief Air Marshal Agus Supriatna said there were no survivors after the plane ploughed into houses and commercial buildings in Medan, the country's third largest city. The plane left Jakarta with 113 people aboard, including military personnel and their relatives, but it was not clear how many continued the journey to Medan after stopovers in Pekanbaru and Dumai, Agus said. (Photo by Dedi Sahputra/EPA)

New York's famed Empire State Building hosted new guests on Saturday night as images of endangered animals were flashed across its facade.