Model Heidi Klum and TV personality Nick Cannon speak onstage during Nickelodeon's 24th Annual Kids' Choice Awards at Galen Center on April 2, 2011 in Los Angeles, California. (Photo by Kevork Djansezian/Getty Images)

An Aden civilian crouching in terror as British soldiers threaten him during Arabian demonstrations in Crater. (Photo by Express Newspapers/Getty Images). 1967

Tsar Alexander II (1818–1881) known as “The Liberator” lying in state. He was mortally wounded by an assassination attack in St Petersburg. (Photo by Hulton Archive/Getty Images). March 1881

A detail of "Supersilvio" by Francesco De Molfetta representing the Italian Prime Minister Silvio Berlusconi is displayed during the MiArt 2011 Contemporary and Modern Art International Fair press preview on April 7, 2011 in Milan, Italy.

Workers sort freshly-painted Easter eggs at the Lueck poultry farm on April 7, 2011 in Sommerkahl near Aschaffenburg, Germany. The farm is currently working 24-hour shifts to meet demand for its brightly-coloured eggs two weeks before Easter. (Photo by Ralph Orlowski/Getty Images)

Blue Man Group founders Phil Stanton, Chris Wink and Matt Goldman pose for a photo at the Blue Man Group's 20th anniversary reunion show to benefit The Blue School at the Astor Theater on April 13, 2011 in New York City.

Actress Tanga Chisholm (L) and actor Stephen Kramer Glickman attend the Ok! Magazine Toasts Hollywood's Sexiest Singles event at the Lexington Social House on April 14, 2011 in Hollywood, California. (Photo by Frederick M. Brown/Getty Images)

Three workers demonstrating the different types of gas masks used in mine rescue work. (Photo by Fox Photos/Getty Images). December 1925