Fighters of the Free Syrian Army fire an anti-aircraft weapon in the rebel-held Mashhad area in southeastern Aleppo, on December 12, 2016, as they battle Syrian government forces during an operation to retake the embattled city. The crucial battle for Aleppo entered its “final phase” after Syrian rebels retreated into a small pocket of their former bastion in the face of new army advances. The retreat leaves opposition fighters confined to just a handful of neighbourhoods in southeast Aleppo, the largest of them Sukkari and Mashhad. (Photo by AFP Photo/Stringer)

A participant poses with his laptop during the 33rd Chaos Communication Congress on its opening day on December 27, 2016 in Hamburg, Germany. The annual event is bringing together 12,000 computer hackers and activists who will meet over the next four days to share expertise and discuss topics related to the society and the digital world. (Photo by Morris MacMatzen/Getty Images)

Soldiers are reflected in a puddle during a military parade during the celebrations for Romania's National Day in Bucharest December 1, 2014. (Photo by Radu Sigheti/Reuters)

A demonstrator attends a protest against fare hikes for city buses in Rio de Janeiro January 16, 2015. Amid a marked economic downturn and high inflation, bus fares went up in Sao Paulo, Brazil's largest city, from 3 to 3.50 reais, and in Rio, the former capital, from 3.0 to 3.40 reais. (Photo by Mauro Pimentel/Reuters)

Riot Police form a cordon as a Police car burns on the opening day of the European Central Bank (ECB) in Frankfurt am Main, western Germany, on March 18, 2015. Supporters of the so-called Blockupy alliance consisting of social movements, activists, workers, trade unions and parties are expected to stage large protests against austerity and the authority of the European Central Bank when the bank's new headquarters officially will be on March 18, 2015. (Photo by Odd Andersen/AFP Photo)

These images give a rare insight into the life of a 19th Century Indian Maharajah. Maharajah Ram Singh ruled in the famous pink city of Jaipur between 1835 and 1880, and was also a keen photographer. Here: Full portrait of a woman in the harem in the royal palace of Jaipur, India, 1857 – 1865. (Photo by Maharaja Ram Singh III/Alinari via Getty Images)

Group of blow-up dolls and women. (Photo by Zomi/Getty Images)

A man sits waiting for a train on the London Underground in 1890, when the platform floors were still made from wooden floorboards. (Photo by Hi-Story/Alamy Stock Photo)