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 boy jumps over a puddle of water on the outskirts of Havana, Cuba March 21, 2016. (Photo by Ueslei Marcelino/Reuters)

Two female holidaymakers relax on an unidentified beach of England, September 21, 1940, as a soldier, eyes straight ahead, stands guard at a barrier built as a defense against possible invasion by Germany. (Photo by AP Photo)

Members of the media film as a ranger performs a post mortem on the carcass of a rhino after it was killed for its horn by poachers at the Kruger national park in Mpumalanga province August 27, 2014. Rhino poachers in South Africa now risk giving themselves away when they shoot thanks to a high-tech, gunfire-detection system being piloted in the country's flagship Kruger National Park. The stakes are high, for rhinos are being slain in escalating numbers for their prized horns, alarming both conservationists and the government since wildlife in South Africa is an important tourist draw. (Photo by Siphiwe Sibeko/Reuters)

Andrew Newey, an award-winning UK-based travel photographer, has captured gripping photographs of central Nepalese Gurung tribe members engaged in a dangerous and ancient tradition – honey hunting.

In this Sunday, March 2, 2014 photo, animal barber Mohamed Mahmoud shaves a customer's initials onto the rump of a donkey in Cairo, Egypt. Clients typically request for regular trims to keep animals cool in the summer, initials in English letters, and patterns – but sometimes they give Mahmoud full creative license. (Photo by Maya Alleruzzo/AP Photo)

Triplet sisters Natalia, Irina and Tatiana Mironenko attend a rehearsal while preparing for examination performances staged by the graduates of the folk dance faculty of the Krasnoyarsk choreographic college in Krasnoyarsk, Russia May 13, 2019. All three 19-year-old sisters are expected to join the renowned Krasnoyarsk state academic dance ensemble of Siberia after the graduation. (Photo by Ilya Naymushin/Reuters)

Italy’s Alessia Trost reacts after competing in the women’s high jump during the World Athletics Championships in Doha, Qatar on September 27, 2019. (Photo by Aleksandra Szmigiel/Reuters)