These adorable cats – which are twins – showcase their contrasting blue and green eyes. The cats have a condition called heterochromia iridis, which causes each eye to vary in color. (Photo by @sis.twins/Caters News Agency)

A Taiwanese woman takes a photo of a Christmas tree decoration at a street in Taipei, Taiwan,13 December 2015. (Photo by Ritchie B. Tongo/EPA)

A group of volunteers dressed as elves and a man dressed as the grinch take part in a Christmas celebration organised by the NGO “Unos Venezolanos” in the neighbourhood of Petare, in Caracas, Venezuela on December 21, 2022. (Photo by Gaby Oraa/Reuters)

In northwest Russia, in a small village called Alekhovshchina, Nadia Sablin's aunts spend the warmer months together in the family home and live as the family has always lived, chopping wood to heat the house and making their own clothes. Sablin's book of photographs, “Aunties: The Seven Summers of Alevtina and Ludmila”, is published by Duke University Press. Here: “Two-Handed Saw, 2014”. (Photo by Nadia Sablin)

Britain's Health and Social Care Secretary Matt Hancock wears Union Jack socks as he leaves with Britain's Leader of the House of Lords Baroness Evans after a cabinet meeting on Downing Street in London, Britain on January 7, 2020. (Photo by Toby Melville/Reuters)

Lindsey Stirling performs onstage at Salle Pleyel on December 19, 2023 in Paris, France. (Photo by Kristy Sparow/Getty Images)

Principle Ballet Dancer, Ekaterina Bulgutova, of the Russian State Ballet, with the Nutcracker part of Christmas Ballet Season in Cardiff which starts at St Davids Hall on December 20, 2016 in Cardiff, England. (Photo by Kiran Ridley/Barcroft Images)

A swimmer goes for a dip in freezing temperatures at the Serpentine Lake in Hyde Park, central London on December 1, 2023, as temperatures in the capital dip below zero for another night. The Met Office has issued a yellow weather warning for parts of the UK with freezing temperatures and snow expected in large areas. (Photo by Ben Cawthra/London News Pictures)