A girl smiles as her hair is blown by a strong wind in the Chinatown area in Yokohama, near Tokyo, Friday, January 27, 2017. (Photo by Koji Sasahara/AP Photo)

Rebecca Bailey rides a unicycle during a winter nor'easter snow storm in Boston, Massachusetts, U.S. February 9, 2017. (Photo by Brian Snyder/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)

US freestyler, gold medalist Mcrae Williams competes during the men' s SlopeStyle (SS) finals at the FIS Snowboard and Freestyle Ski World Championships 2017 in Sierra Nevada on March 19, 2017. (Photo by Albert Gea/Reuters)

A Romanian female soldier adjusts her helmet before taking part in weapons training with US Marines female counterparts at the Capu Midia Surface to Air Firing Range, on the Black Sea coast in Romania, Monday, March 20, 2017. About 1,200 US and Romanian troops take part in the Spring Storm 17 exercise, meant to simulate defense of the Romanian Black Sea coastline and urban areas. (Photo by Vadim Ghirda/AP Photo)

In this April 20, 2017 photo, a woman is aided by fellow demonstrators after falling, overcome by tear gas, during anti-government protests in Caracas, Venezuela. Tens of thousands of protesters asking for the resignation of President Nicolas Maduro flooded the streets again, one day after three people were killed and hundreds arrested in the biggest anti-government demonstrations in years. (Photo by Ariana Cubillos/AP Photo)

A Palestinian man rides his horse on a beach in Gaza City February 17, 2017. (Photo by Mohammed Salem/Reuters)

A Muslim man carries holy incensed smoke through a pedestrian subway in Mumbai, India, May 13, 2016. (Photo by Danish Siddiqui/Reuters)