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)

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)

Women sits outside a go-go dance bar in Pattaya, Thailand March 25, 2017s. (Photo by Jorge Silva/Reuters)

Auditioning performers follow resident choreographer Erik Sorensen, center back, at the Sydney Dance Company in a routine during castings in Moulin Rouge's current show “Féerie”, in Sydney, Australia, Thursday, July 28, 2016. The show's artistic team is in Australia to choose new talent to perform with one of the most famous cabarets that has been illuminating Paris since 1889. (Photo by Rob Griffith/AP Photo)

A combination photo shows various popular street foods under $6 from various hawker food stalls and eateries in Singapore, taken between July 28 to 31, 2016. Top row (L to R) bak chor mee, soya sauce chicken; Middle row (L to R) laksa, hokkien mee, nasi lemak, ice kachang; Bottom row (L to R) rojak, roti prata and satay. (Photo by Edgar Su/Reuters)

An Indian priest worships six-year-old Hindu girl Anushka Chetterjee dressed as the Hindu goddess Durga at a “pandal” for the celebrations of the “Durga Puja” festival in Kolkata on September 28, 2017. The five-day Durga Puja festival, which commemorates the slaying of the demon king Mahishasur by the goddess Durga, marks the triumph of good over evil. (Photo by Dibyangshu Sarkar/AFP Photo)

Women perform under black fabric during a street performance in Pristina on October 6, 2017 against sexual harassments in Kosovo. (Photo by Armend Nimani/AFP Photo)

Antonina Yermokhina, 86, does physical exercises during her daily training session on the embankment of the Yenisei River in the Siberian town of Divnogorsk, Russia November 13, 2017. (Photo by Ilya Naymushin/Reuters)