Mrs. Marie Graskamp of Milwaukee shows the different positions one might assume when entering the bomb shelter in Milwaukee September 3, 1958. This circular entrance is about three feet in diameter. This is the entrance (according to the builders) that would connect to the cellar of a home assuming the shelter was in the ground for added protection. If a bombing should occur, all members of family would proceed to the cellar and then through the circular port into the shelter. (Photo by AP Photo)

In this September 16, 1983 file photo, actor and bodybuilder Arnold Schwarzenegger shows off his new U.S. citizenship papers as Maria Shriver, daughter of Sargent and Eunice Shriver, looks on at the Shrine Auditorium in Hollywood, Calif. (Photo by Wally Fong/AP Photo)

Londoners sleep on the platform and on the train tracks at Aldwych Underground station,London, during heavy all night Nazi bombing raids, October 8, 1940. (Photo by AP Photo)

A zoo employee carries three-month-old female giant panda cub, born to mother Liang Liang and father Xing Xing, on display to the public for the first time at the national zoo in Kuala Lumpur, Malaysia, November 17, 2015. (Photo by Olivia Harris/Reuters)

A bonnet macaque sits on consecrated idols of snakes during the Nag Panchami festival inside a temple on the outskirts of Bengaluru, India, August 19, 2015. (Photo by Abhishek N. Chinnappa/Reuters)

Whether they are the hunter or the hunted, these camouflage animals show natures incredible ability to blend in with its surroundings. Pictured perfectly concealed against their natural environment, the stunning pictures show the amazing lengths some animals will go to to stay out of sight. Here: The camouflage mappet moth looks like a fall lead in Switzerland. (Photo by Thomas Marent/Caters News/Ardea)

Attendee Emily poses for a picture at 2017 Comic-Con International on July 20, 2017 in San Diego, California. (Photo by Mike Blake/Reuters)

A gray heron (Ardea cinerea) that fished a common carp (Cyprinus carpio) in Geneva, Switzerland, 21 April 2019. (Photo by Martial Trezzini/EPA/EFE/Rex Features/Shutterstock)