A Somali police officer arrests a suspected rebel member of the al Qaeda-affiliated al Shabaab among beach goers in Mogadishu. Al Shabaab claimed responsibility for today's pre-dawn attack on a Kenyan university campus near the Somali border. The following gallery examines who is al Shabaab. Here: Somali police officer (R) arrests a suspected rebel member (L) of the Al Qaeda-affiliated al Shabaab among beach goers at the Lido beach north of Somalia's capital Mogadishu March 23, 2012. (Photo by Feisal Omar/Reuters)

An Israeli army officer gives explanations to journalists during an army organised tour in a tunnel said to be used by Palestinian militants for cross-border attacks, July 25, 2014. (Photo by Jack Guez/Reuters)

Circus performer and trampolinist Max Calaf Seve performs at a preview for NoFit State Circus new summer show at the Eden Project on March 29, 2012 in St Austell, England. This will be the second time that the NoFit Circus has performed in the world famous biomes of the Eden Project. The production will start on July 28 and run until September 2 before leaving Cornwall for a global tour. (Photo by Matt Cardy/Getty Images)

Toddlers by Karolina Bazydlo. (Photo by Karolina Bazydlo; Source: Flickr)

Backdropped by a night time view of the Earth and the starry sky, the Space Shuttle Endeavour is seen docked to the International Space Station on May 28, 2011. (Photo by Reuters/NASA)