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 reveler, dressed as a Brazilian national army soldier holding a mock weapon with flowers jutting out of it, participates in the annual Gay Pride Parade in Sao Paulo, Brazil, Sunday, June 18, 2017. (Photo by Nelson Antoine/AP Photo)

A man pushes her daughter on a cart as they shop at a market in Seoul, South Korea, July 26, 2016. (Photo by Kim Hong-Ji/Reuters)

Actors Ma Sichun (L) and Zhou Dongyu pose backstage after both won the Best Leading Actress award for their movie “Soul Mate” at the 53rd Golden Horse Film Awards in Taipei, Taiwan November 26, 2016. (Photo by Tyrone Siu/Reuters)

A Kashmiri villager shouts freedom slogans during the funeral procession of Asadullaha Kumar in Mandhaal village, some 70 Kilometers south of Srinagar, Indian controlled Kashmir, Saturday, December 3, 2016. Hundreds of angry villagers blocked the Srinagar-Jammu highway for hours alleging Kumar was tortured and then shot by Indian forces while he was performing his duty as a security guard at a government fishery. Police officers denied the allegation and said he was killed in cross-firing during an overnight counter-insurgency operation in south Kashmir. (Photo by Dar Yasin/AP Photo)

A woman uses a virtual reality (VR) headset to view images by Mexican painter Frida Kahlo in Mexico City, Mexico, 23 May 2018. The technological giant Google launched the “The Faces of Frida”, an interactive digital exhibition that treasures the heartrending work of the Mexican artist to tell her story from different points of view, with attention to the invisible details. (Photo by Sashenka Gutierrez/EPA/EFE)

In this 1997 photo released by the International Fund for Animal Welfare, a seal hunter, right, threatens a cameraman with a knife during the filming of a seal hunt in the Gulf of St. Lawrence, Canada. “Huntwatch”, a documentary by the organization about the fight to end commercial seal hunts, premieres in September 2016 on Discovery. The producers say it includes grainy but powerful archive footage that had languished in the basement of the group’s headquarters on Cape Cod for nearly five decades. (Photo by Richard Sobol/IFAW via AP Photo)

A tattoo artist applying ink on a girl's thigh at the 2016 Italian Tattoo Artists at the Palavela on September 17, 2016 in Turin, Italy. (Photo by Stefano Guidi/ZUMA Press/Splash News)