Two stags fight in a wildlife park in Aurach near Kitzbuehel, in the Austrian province of Tyrol. (Photo by Kerstin Joensson/Associated Press)

Gabriella Papadakis and Guillaume Cizeron of France perform during the ice dance skating event at the ISU Grand Prix of Figure Skating final in Barcelona December 13, 2014. (Photo by Albert Gea/Reuters)

A man strikes a pose in front of a giant torta, or sandwich, during a press conference to promote the 13th annual Torta Festival, in Mexico City, Wednesday, July 20, 2016. The five day festival presents a variety of the Mexican street food made from the most exotic ingredients that include ostrich or stingray, to the classic ham, grilled steak or slow cooked pork. The festival's purpose is to maintain the tradition of eating tortas, and promote the vendors of the Mexican sandwich. (Photo by Marco Ugarte/AP Photo)

A lunar eclipse appears behind a gargoyle atop the old red Dallas County Courthouse early Wednesday morning, October 8, 2014. The moon appears orange or red, the result of sunlight scattering off Earth's atmosphere. This is known as the blood moon. (Photo by Tom Fox/AP Photo/The Dallas Morning News)

Monaco's Princess Charlotte Casiraghi arrives to attend a mass at the Saint Nicholas Cathedral during the celebrations marking Monaco's National Day, on November 19, 2016 in Monaco. (Photo by Valery Hache/Reuters)

28 year old Rupa has her hair shaven to donate to the Gods at the Thiruthani Murugan Temple November 10, 2016 in Thiruttani, India. Rupa donated her hair with the wish that her daughter's illness is cured. The process of shaving ones hair and donating it to the Gods is known as tonsuring. It is common for Hindu believers to tonsure their hair at a temple as a young child, and also to celebrate a wish coming true, such as the birth of a baby or the curing of an illness. The “temple hair”, as it's known, is then auctioned off to a processing plant and then sold as pricey wigs and weaves in the US, Europe and Africa. (Photo by Allison Joyce/Getty Images)

A fan of Serbia scuffles with Albania's Mergim Mavraj during their Euro 2016 Group I qualifying soccer match at the FK Partizan stadium in Belgrade October 14, 2014. The Euro 2016 qualifier between Serbia and Albania was abandoned on Tuesday following a brawl between players from both sides. (Photo by Marko Djurica/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)