A coil-shaped Helix Nebula showing a fine web of filamentary “bicycle-spoke” features embedded in the colorful red and blue ring of gas. At 650 light-years away, the Helix is one of the nearest planetary nebulae to Earth. A planetary nebula is the glowing gas around a dying, Sun-like star. (Photo by Reuters/NASA)

The selfie is the most popular photography trend of the internet today. It's gotten so popular, in fact, that even our beloved feline friends have started to catch on. I dare you to keep the smile off your face for this one!

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.

Model Irina Shayk attends the screening of “Sorry Angel (Plaire, Aimer Et Courir Vite)” during the 71st annual Cannes Film Festival at Palais des Festivals on May 10, 2018 in Cannes, France. (Photo by George Pimentel/WireImage)

Bollywood actress Sonam Kapoor arrives for the Giorgio Armani women's 2019 Spring-Summer collection during the Milan Fashion Week, in Milan, Italy, 23 September 2018. The Spring Summer 2019 Women's collections are presented at the Milano Moda Donna from 19 to 24 September. (Photo by Matteo Bazzi/EPA/EFE)

Rita Ora leaving her hotel to go to BBC Children in need on November 07, 2018 in London, England. (Photo by Mark R. Milan/GC Images)

A reveller from Unidos da Tijuca samba school performs during the second night of the carnival parade at the Sambadrome in Rio de Janeiro, Brazil, February 28, 2017. (Photo by Ricardo Moraes/Reuters)

Cardi B performs at the “Night Two At Palms Casino Resort's KAOS Dayclub & Nightclub With Cardi B, G-Eazy, J Balvin For Grand Opening Weekend” event on April 6, 2019 in Las Vegas, Nevada. (Photo by Roger Kisby/Getty Images for Palms Casino Resort)