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 giant size figure of the United States' goalkeeper Tim Howard is displayed outside a shopping mall in Hong Kong, Thursday, June 12, 2014, to promote the upcoming 2014 World Cup in Brazil. A total of seven 3.5 meters to 4 meters (11 feet 6 inch to 13 feet one inch) tall figures of famous players attract many soccer fans. (Photo by Vincent Yu/AP Photo)

This photo taken on August 7, 2016 shows mahjong enthusiasts playing mahjong under water in a swimming pool at a diving club in the Chinese city of Chongqing. Only participants with proper diving certification were allowed to take part in the underwater competition. (Photo by AFP Photo/Stringer)

A toddler sits on the winner of the giant pumpkin category during the RHS (Royal Horticultural Society) London Harvest Festival Show at RHS Lindley Halls on October 6, 2015 in London, England. The traditional harvest themed show runs October 6-7 and showcases a wide range of late summer grown fruit and vegetables. (Photo by Ben Pruchnie/Getty Images)

Athlets run during the women's 3000 meter steeplechase at the International Athletics Meeting in Lucerne, Switzerland, 14 June 2016. (Photo by Alexandra Wey/EPA)

A masked protester talks to a soldier during clashes after the funeral of Brig. Gen. Wissam al-Hassan October 21, 2012. Lebanese soldiers fired guns and tear gas to push back hundreds of protesters who broke through a police cordon and tried to storm the government headquarters in Beirut. (Photo by Hussein Malla/Associated Press)

Dancers Daisy Kerry (R) and Alice Rathbone pose as characters from The Nutcracker, for the annual Christmas event at Chatsworth House near Bakewell in Britain November 4, 2016. (Photo by Darren Staples/Reuters)

A reveler wearing sheepfur costume is seen in front of a bonfire on which they burn a coffin symbolizing winter during the closing ceremony of the traditional carnival parade in Mohacs, 189 kms south of Budapest, Hungary, 07 February 2016. The carnival parade of people, the so-called busos, dressed in such costumes and frightening wooden masks, using various noisy wooden rattlers is traditionally held on the seventh weekend before Easter to drive away winter, and is a revival of a legend, which says that ethnic Croats ambushed the Osmanli Turkish troops, who escaped in panic seeing the terrifying figures during the Turkish occupation of Hungary. (Photo by Tamas Soki/EPA)