Macro or Micro? Scientists’ pictures baffle our sense of scale. It began when Stephen Young, a geography professor at Salem State University in Massachusetts, tricked his biologist colleague Paul Kelly into thinking a satellite image was one of his electron microscope scans. Can you guess whether they are close-up or very far away? (Photo by Paul Kelly)

“These are the mind-blowing artworks of one professor who has dedicated his professional life to studying and generating a series of dizzying optical illusions. Professor Akiyoshi Kitaoka, from Ritsumseikan University, in Kyoto, Japan, has spent more than a decade creating his collecting of stomach-churning works. His designs have been used by the likes of Lady Gaga, who ran the Kitaokas work, entitled Gangaze, as the CD cover for her album Art Pop, in 2013”. – Caters News. (Photo by Akiyoshi Kitaoka/Caters News)

A group of San Bushmen from the Khomani San community practice their hunter-gatherer craft in the Southern Kalahari desert on October 15, 2009 in the Kalahari, South Africa. One of the largest studies of African genetics by an international team from the University of Pennsylvania, published in April 2009, revealed that the San of Southern Africa are the most genetically diverse on earth, and that the San homeland could be the spot where modern humanity began. (Photo by Dan Kitwood/Getty Images)

Final preperations are made backstage during Graduate Fashion Week at Earls Court on June 6, 2011 in London, England. The event which began in 1991 showcases emerging talent from BA Graduate fashion design courses across the UK and includes exhibition stands and catwalk shows from around 50 universities. (Photo by Dan Kitwood/Getty Images)

Singer Zendaya arrives at the 2015 American Music Awards in Los Angeles, California November 22, 2015. (Photo by David McNew/Reuters)

A muddied family photograph sits on a hallway stairwell in an apartment block on March 17, 2011 in Kensennuma, Japan. Residents were allowed back to their homes today and began the massive cleanup operation caused by a 9.0 magnitude strong earthquake that struck on March 11 off the coast of north-eastern Japan. The quake triggered a tsunami wave of up to 10 metres which engulfed large parts of north-eastern Japan. The death toll has risen past 5000 with at least 8600 people still missing. (Photo by Chris McGrath/Getty Images)

Throughout the course of the long war in Afghanistan, Coalition troops have relied on thousands of military working dogs to help keep them safe, and make their jobs easier. The dogs are trained to detect explosives, to find illegal drugs, to search for missing comrades, or target enemy combatants. Not only are they active on the front lines, but behind the lines they serve as therapy dogs, service dogs, and loyal companions. They also share the same risks as the ground troops, suffering injuries and sometimes death on the battlefields. Gathered here are images of these dogs and their handlers in Afghanistan and back home, from over the past several years, part of the ongoing series here on Afghanistan.