A villager pours brine into troughs at ancient salt fields on May 5, 2005 in Yantian Village on Hainan Island, China. (Photo by China Photos/Getty Images)

Monks take a tiger out of its cage for an afternoon walk June 5, 2001 at the Wat Pa Luangta Bua monastery in Kanchanaburi, Thailand. (Photo by Paula Bronstein/Getty Images)

The two dogs Travis, 10, and Gus, 5 have become an Internet hit on Instagram. These images were taken by Canadian photographer Steph McCombie. (Photo by Steph McCombie/Instagram)

An Indian student warms up during the 44th Samartha Summer Sports Coaching Camp organized by Shree Samarth Vyayam Mandir in Mumbai, India, 25 April 2018. Mallakhamba arose in the western state of Maharashtra centuries ago. It was originally practiced by wrestlers and soldiers as a strength training exercise. (Photo by Divyakant Solanki/EPA/EFE)

A man passes by an unfinished street art graffiti made in a stairway by French street artists Zag and Sia in Paris on March 1, 2016. The two artists drew inspiration from famous “Liberty Leading the People” (La Liberte guidant le peuple) painting by French Eugene Delacroix commemorating the July Revolution of 1830 and viewed as a symbol of the French Republic. (Photo by Joel Saget/AFP Photo)

Ingots of 99.99 percent pure silver are cast at the Krastsvetmet Krasnoyarsk non-ferrous metals plant in the Siberian city of Krasnoyarsk, Russia, June 5, 2015. Krastsvetmet is one of the world's largest players in the precious metals industry. REUTERS/Ilya Naymushin

In this photo taken on Sunday, July 5, 2015, police officers walk along a giant poster to give an improved appearance, in downtown Ufa, Russia. Ufa will host SOC (Shanghai Cooperation Organization) and BRICS (Brazil, Russia, India, China and South Africa) summits July 7 to July 9, 2015. (Photo by Vadim Braydov/AP Photo)

In this Saturday, September 5, 2015, photo, three women in costumes look at sea life swimming above them during a private party held at the Georgia Aquarium as part of Dragon Con in Atlanta. The convention draws fans from around the country to take part in sci-fi and fantasy costume contests, a massive parade through downtown Atlanta and educational seminars about science and costume making. (Photo by Ron Harris/AP Photo)