Roof-topping enthusiast Daniel Lau takes a selfie with high-rise buildings down below as he stands on the top of a skyscraper in Hong Kong, China on August 15, 2017. A craze that began in Russia has now taken hold in Hong Kong, one of the world's most vertical cities. Mr Lau said he had been inspired by Russian climbers and that he was unafraid of the vertiginous heights he scales. (Photo by ImagineChina/Rex Features/Shutterstock)

A pro-Russian armed man secures crash site wreckage of the Malaysia Airlines Boeing 777 plane (flight MH17) at the site of the plane crash near the settlement of Grabovo in the Donetsk region November 16, 2014. Local emergency services have begun collecting parts of the wreckage from its crash site in the middle of the conflict zone, Dutch air accident investigators said on Sunday. Dutch inspectors had hoped to collect the parts themselves, following the downing of the flight on July 17 that killed 298 people, two thirds of them Dutch citizens. But they remain concerned about the safety of their staff in the rebel-held conflict zone, and so have decided to work with local services following an initial focus on finding human remains and belongings. (Photo by Antonio Bronic/Reuters)

An Israeli boy looks through the sight of a weapon during a display of Israeli Defense Forces (IDF) equipment and abilities at the West Bank settlement of Kiryat Arba, April 23, 2015, during celebrations for Israel's Independence Day, marking the 67th anniversary of the creation of the state. (Photo by Ronen Zvulun/Reuters)

An interactive art installation created by artist Michael Verdon called the “Temple of Essence” dedicated to "victims of the war on drugs" is burned on the U.S. National Mall in front of the Washington Monument in Washington November 22, 2015. People were encouraged to write personal messages on the temple walls and leave mementos behind inside the interactive art piece, which was the centerpiece of a 48-hour vigil called "Catharsis on the Mall: A Vigil for Healing the Drug War". (Photo by Jim Bourg/Reuters)

Vernon Yates, founder of Wildlife Rescue and Rehabilitation, lays his hands on Ty, a 400-pound tiger, as staff prepare to surgically extract a 4-pound hairball from the big cat, in Clearwater, Florida, on May 22, 2013. Ty is cared for by Wildlife Rescue and Rehabilitation in Seminole. The non-profit animal rescue group mainly serves by assisting Florida law enforcement with animals that have been seized. (Photo by James Judge/Courtesy BluePearl Veterinary Partners)

This photo taken on March 29, 2017 shows a young woman offering shots of liquer at a dance bar in Walking Street in Pattaya. Two hours east of Bangkok, Pattaya's bawdy reputation hails from the Vietnam War era when US GIs partied in their downtime. (Photo by Roberto Schmidt/AFP Photo)

Soap Bubble Structures by Kym Cox. Bubbles optimise space and minimise their surface area for a given volume of air. This phenomenon makes them a useful tool in many areas of research, in particular, materials science and “packing” – how things fit together. Bubble walls drain under gravity, thin at the top, thick at the bottom, which interferes with travelling lightwaves to create bands of colour. Black spots show the wall is too thin for interference colours, indicating the bubble is about to burst. (Photo by Kym Cox/2019 Science Photographer of the Year/RPS)

This photo released by the Cleveland Animal Protective League shows Lurleen, the nursing mother and Noland the puppy snuggling up Wednesday, June 19, 2013, in Cleveland. Lurleen already is caring for four newborn kittens and now is nursing the orphaned week-old pit bull puppy in Cleveland. (Photo by AP Photo/Cleveland Animal Protective League)