A woman is tattooed by an artist during Warsaw Tattoo Convention 2014 in Warsaw November 29, 2014. (Photo by Kacper Pempel/Reuters)

A woman holds a skull during a “Dia de los natitas” (Day of the Skull) ceremony at the Cementerio General of La Paz. (Photo by David Mercado/Reuters)

Soldiers take part in a drill during a heavy snow in Heihe, Heilongjiang province, February 26, 2014. (Photo by Reuters/China Daily)

Donna Vekic of Croatia poses during a portrait session held on February 9, 2012 in London. (Photo by Clive Brunskill/Getty Images)

A line of soldiers firing handguns during a training session, circa 1920. (Photo by Keystone). P.S. All pictures are presented in high resolution.

A cadet lies on the grass after collapsing during a promotion ceremony at a police school in Bogota December 7, 2012. (Photo by John Vizcaino/Reuters)

Jorge Diaz punches Teon Kennedy during their USBA Super Bantamweight bout during Top Rank's 'Featherweight Fury' on March 26, 2011 at Boardwalk Hall in Atlantic City, New Jersey.

Artists preform on a pool suspended above the audience during the Fuerza Bruta dress rehearsal on February 1, 2012 in Tel Aviv, Israel. (Photo by Uriel Sinai/Getty Images)