A couple hugs while standing near a Christmas tree made out of plastic bins and plastic hampers outside the Museum of History in Monterrey, Mexico, December 4, 2015. The humble Christmas tree has a rich history, from evergreen trees used to symbolise eternal life in Ancient Egypt to tree worship among pagan Europeans. The modern version has its origins in Germany, where the song “O Tannenbaum” is still a festive favourite. Today the traditional tree with lights and decorations appears in cities including Washington, Moscow and Beirut. Alternative constructions range from recycled rubbish in Mexico City to old window frames in Rakvere, Estonia. Whatever the shape or size, the message is the same: Merry Christmas. (Photo by Neil Hall/Reuters)

Nihon University professor and head of Nihon University Animal Medical Center Kazuya Edamura, 49, points to cat photos on a computer screen, which are used to train the AI of “CatsMe!”, an AI-driven smartphone application jointly developed by tech startup Carelogy and researchers at Nihon University that purports to tell when a cat is feeling pain, as he gives a lecture to students on diagnosing pain in cats, at the medical center in Fujisawa, south of Tokyo, Japan on June 11, 2024. (Photo by Issei Kato/Reuters)

A South African police officer speaks to residents of the densely populated Alexandra township east of Johannesburg Friday, March 27, 2020. (Photo by Jerome Delay/AP Photo)

A man wearing a face mask walks past a picture of a Russian tank in central Moscow on June 18, 2020. Russia's President Putin on June 24 will preside over a massive military parade to mark Soviet victory in World War II, which was postponed due to the coronavirus pandemic. (Photo by Yuri Kadobnov/AFP Photo)

Dancers of the Palestinian Jafra Dabke Team perform a traditional dabke dance while wearing latex gloves and surgical masks for people confined due to a COVID-19 coronavirus pandemic lockdown in the village of Tarqumia northwest of Hebron in the occupied West Bank, on April 15, 2020. (Photo by Hazem Bader/AFP Photo)

A woman walks in a street in freezing weather of –24 degrees Celsius in Omsk, Russia on January 13, 2021. Daytime temperatures have been below –20 degrees Celsius in the Omsk Region since 25 December 2020. (Photo by Yevgeny Sofiychuk/TASS)

People pose for photos among a field of cosmos flowers in a car park before high-rise apartment buildings in Goyang, west of Seoul on September 22, 2020. (Photo by Ed Jones/AFP Photo)

People spray water in the street ahead of “Songkran”, the annual Thai New Year water-throwing festival, in Kowloon City, Hong Kong, China, 09 April 2017. The pouring of water is a key element in the festival as it represents purification and the washing away of one's sins and bad luck for the year. The event also includes a “Miss Songkran” pageant where contestants are clothed in traditional Thai dress, and a winner is crowned. This year's “Songkran” will begin in Thailand on 13 April 2017. (Photo by Alex Hofford/EPA)