A woman cries after a supporter of opposition leader Raila Odinga was killed by police, witnesses said, in Mathare slum in Nairobi, Kenya August 9, 2017. (Photo by Goran Tomasevic/Reuters)

Brain-on-a-chip. Dazzling in green and magenta this image shows the nerve fibres (in green) produced by neural stem cells (in magenta) as they grow on a synthetic gel. Captured by a technique known as confocal microscopy, the image is part of research shedding light on how tinkering with the environment can affect the way in which nerve fibres grow. (Photo by Collin Edington and Iris Lee/Massachusetts Institute of Technology/Wellcome Images)

A kid wearing rollerblades hitches a ride via motorbike, in Port-au-Prince, Haiti, Sunday, October 25, 2015. The country held the first-round presidential vote Sunday. Haitians chose between 54 presidential hopefuls and a slew of legislative and municipal candidates. (Photo by Ricardo Arduengo/AP Photo)

A general view of the sunrise over Hawes, Wensleydale, UK on November 24, 2014. (Photo by Neil Squires/PA Wire)

American Yoga teacher Dashama poses on a Yoga-board during a preview of the 46th International Boat Fair in Duesseldorf January 16, 2015. The BOOT 2015 watersports fair, with more than 1,600 international exhibitors will run in Duesseldorf from January 17 to January 25. (Photo by Ina Fassbender/Reuters)

Shoppers walk past crocodiles for sale at a market in Bata on February 3, 2015. Markets in Equatorial Guinea sell a variety of animals including pangolins, monkeys and crocodiles as food. (Photo by Carl De Souza/AFP Photo)

Dillon Bracken (L) and Atalya Stachel dance during the Burning Man 2014 “Caravansary” arts and music festival in the Black Rock Desert of Nevada, August 30, 2014. Over 65,000 people from all over the world have gathered at the sold out festival to spend a week in the remote desert cut off from much of the outside world to experience art, music and the unique community that develops. (Photo by Jim Urquhart/Reuters)

A 210-kilogram-weight Epinephelussp was showed at China Fisheries & Seafood Expo in Fuzhou, Fujian, China on 24th October, 2014. (Photo by Top Photo/Sipa Press USA)