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)

Devotees wear costumes made of banana leaves as they head to church to attend mass as part of a religious festival, in honor of St. John the Baptist, also known locally as the “mud people” festival, in Aliaga town, Nueva Ecija province, north of Manila, on June 24, 2017. Farmers coated in mud paraded in Philippine villages on June 24 to mark one of the Catholic nation's most colourful religious festivals. (Photo by Noel Celis/AFP Photo)

In a July 14, 1967 file photo, left, National Guardsmen make their way along Market Street in Newark, N.J, after an evening of deadly rioting and looting in what came to be known as the Newark riots. In a June 16, 2017 photo, right, an ambulance drives on the same block 50 years later. (Photo by AP Photo/File, left; Julio Cortez, right)

New lovebirds boxer Robin Deakin – once known as “Britain's Worst Boxer” – and former UK “Big Brother” star Lisa Appleton go to the boxing gym in London, United Kingdom on September 28, 2016. The pair were seen holding hands in the street on arrival, and they then slogged it out in the ring and fooled about in Robin's gym. (Photo by FameFlynet UK)

A Pakistani devotee dances to celebrate the three-day annual festival to pay tribute to the famous saint Al-Sheikh Ali Bin Usman Al-Hajveri known as Data Ganjbaksh at outside his shrine in Lahore, Pakistan, Sunday, November 20, 2016. Thousands of people traveled from all over Pakistan to attend the celebrations. (Photo by K.M. Chaudary/AP Photo)

A fisherman sorts his net next to the 37-meter-long “KAWS:HOLIDAY Companion” inflatable sculpture in Tsing Yi, Hong Kong, China, 21 March 2019. KAWS:HOLIDAY, made by US artist and designer Brian Donnelly known professionally as Kaws, will be displayed in Hong Kong's Victoria Harbour from 22 to 31 March 2019. (Photo by Jerome Favre/EPA/EFE)

A Broto dancer prepares himself in a disused house of Bambari, in the centre of Central African Republic, before performing on March 14, 2019. The Broto, belonging to the Banda ethnic group, are known for their traditional dances accompanied by heavy horns made of tree roots. Today this tradition falls into disuse and its history is now forgotten by the new generations. (Photo by Florent Vergnes/AFP Photo)

A Palestinian man takes a selfie picture next to a camel at a livestock market in the West Bank city of Hebron on August 9, 2019, as muslims prepare for the Eid al-Adha celebrations. Known as the “big” festival, Eid Al-Adha is celebrated each year by Muslims sacrificing various animals according to religious traditions, including cows, camels, goats and sheep. (Photo by Hazem Bader/AFP Photo)