Spacewalker Mark Vande Hei took his own photograph during the first spacewalk of 2018, on January 23, 2018. These sky-high pictures are better known as “space-selfies”. (Photo by Mark Vande Hei/NASA)

A zoo worker feeds milk to tiger cubs born on the first day of the Lunar New Year and Year of the Rooster at Sriracha Tiger Zoo in Chonburi province, Thailand, January 30, 2017. (Photo by Athit Perawongmetha/Reuters)

A participant of the sled dogs race in action with the dogs in Stroehen (Lower Saxony), Germany, 18 October 2015. It is the first round of the North German Championship. (Photo by Peter Steffen/EPA)

Indigenous women from the Kamayura tribe take part in a demonstration of Huka Huka fight at the first World Games for Indigenous Peoples in Palmas, Brazil, October 29, 2015. (Photo by Ueslei Marcelino/Reuters)

A member of the United Arab Emirates armed forces gestures as the first batch of UAE military personnel returns from Yemen in Abu Dhabi, November 7, 2015. (Photo by Reuters/United Arab Emirates News Agency WAM)

Chihuahua Cooper Babb is dressed in a costume at the 7th annual Running of the Chihuahuas event on May 3, 2014, at the First Tennessee Pavilion in Chattanooga, Tenn. (Photo by Doug Strickland/AP Photo/Chattanooga Times Free Press)

Jeff and Kelly Lyons clear the first obstacle while competing in the North American Wife Carrying Championship at Sunday River ski resort in Newry, Maine October 11, 2014. (Photo by Brian Snyder/Reuters)

A man holds the new iPhone 4S after being one of the first customers in the Apple store in Covent Garden on October 14, 2011 in London, England. The widely anticipated new mobile phone from Apple has seen customers queue in cities around the world for hours to be amongst the first to buy the device. (Photo by Oli Scarff/Getty Images)