A photographer tested the concentration of several pairs of dogs as he captured their reactions to treat time in a series of shots. Christian Vieler, 47, of Waltrop, Germany, has been a professional dog photographer since 2016. He came up with the idea of snapping two dogs catching treats simultaneously. Here: Basset Hounds. (Photo by Vieler Photography/Caters News Agency)

These tiny insects are so well camouflaged it is nearly impossible to make out their cleverly disguised forms. Canadian photographer and adventurer Paul Bertner attempted to catch the bugs in their natural habitats as part of a hide-and-seek game to show biodiversity in nature. Here: Stick insects. (Photo by Paul Bertner/Caters News)

A model has her hair done before The Blonds Spring/Summer 2016 collection during New York Fashion Week in New York September 16, 2015. (Photo by Carlo Allegri/Reuters)

A model backstagee is pictured before the Philipp Plein Spring/Summer 2016 collection during Milan Fashion Week in Italy September 23, 2015. (Photo by Alessandro Garofalo/Reuters)

Ariel Winter attends the 4th Annual Just Jared Summer Bash on August 13, 2016 in Los Angeles, California. (Photo by JB Lacroix/Getty Images)

Models on the catwalk Yeezy: Season 4 show, Spring Summer 2017, New York Fashion Week, USA on September 7, 2016. (Photo by Your Name/BFA/Rex Features/Shutterstock)

A model waits backstage before the Spring/Summer 2017 Fashion Palette show at New York Fashion Week in Manhattan, New York, U.S., September 8, 2016. (Photo by Andrew Kelly/Reuters)