Freshmen in Zhengzhou Institute of Aeronautical Industry Management head bottles of mineral water for upright stand during military training on September 17, 2015 in Zhengzhou, Henan Province of China. More than 6,800 freshmen in the school are required to take part in the military training. (Photo by ChinaFotoPress/ChinaFotoPress via Getty Images)

A Palestinian youth demonstrates his parkour skills on a street in Gaza City, January 15, 2016. (Photo by Suhaib Salem/Reuters)

Vietnam’s Son Doong cave, the largest in the world, could hold a 40-story skyscraper inside. The pristine ecosystem has its own river and jungle. Despite its size, Son Doong wasn’t discovered until 1991. It was lost again for nearly two decades and was fully explored for the first time in 2009. (Photo by Jason Speth/HuffPost)

Natalie Portman and Tessa Thompson speak at the Marvel Studios Panel during 2019 Comic-Con International at San Diego Convention Center on July 20, 2019 in San Diego, California. (Photo by Kevin Winter/Getty Images)

Christie Brinkley is seen walking in midtown on August 21, 2019 in New York City. (Photo by Raymond Hall/GC Images)

Kenichi Ito runs on his arms and legs on a race course on his way to setting the Guinness World Record fastest time for the 100-meter dash on all fours at Komazawa Olympic Park Stadium in Tokyo Thursday, November 14, 2013. The 30-year-old Japanese finished in 16.87 seconds Thursday, shaving more than half a second off his 2012 run of 17.47. (Photo by Shizuo Kambayashi/AP Photo)

Iceland is known as the land of fire and ice and these images capture the essence of that perfectly. Incredible ever-changing landscapes demonstrate the contrast between the freezing ice and burning skies that dominate Iceland's beauty. The stunning pictures taken by photographer Lurie Belegurschi show the breathtaking and utterly unique ice plains formed in sub-zero temperatures. (Photo by Lurie Belegurschi/Caters News)

The lightest material ever made has been produced by a team of scientists in China, a Chinese university announced.