A caiman in the Pantanal region of Brazil in 2021. They are used to seeing humans, allowing the photographer, Leighton Lum, a close-up shot. (Photo by Leighton Lum/Caters News Agency)

Third place: the rear leg, claw and respiratory trachea of a louse (Haematopinus suis). (Photo by Frank Reiser/Nassau Community College/Nikon Small World Photomicrography 2021)

A Bengal tigress who gave birth to four cubs at the Guadalajara Zoo, Jalisco state, Mexico runs at the zoo on October 5, 2021. (Photo by Ulises Ruiz/AFP Photo)

A Romanian honor guard soldier waits before the arrival of Moldovan President at Cotroceni Presidential Palace, in Bucharest, Romania, 23 November 2021. Maia Sandu is on a one-day official visit to Romania. (Photo by Robert Ghement/EPA/EFE)

Aubrey Zimmermann, 9-months-old, poses for a photo with Santa at the Willow Grove Park Mall ahead of Christmas in Willow Grove, Pennsylvania, U.S. December 3, 2021. (Photo by Hannah Beier/Reuters)

A Typhoon jet flown by Flt Lt Jim Peterson practising over RAF Coningsby in the East Lindsey district of Lincolnshire, England on September 27, 2019 producing a rainbow effect over the plane. The rainbow is made of crystalized or frozen water vapor that reflect and refract sunlight, causing the rainbow effect. (Photo by Claire Hartley/Bav Media)

Carnival revelers perform during the Academicos do Baixo Augustaa carnival “bloco” parade in Sao Paulo, Brazil, Sunday, February 24, 2019. (Photo by Andre Penner/AP Photo)

A member of Korean Federation for Environmental Movement in a Santa Claus outfit attaches dumped cigarette butts at a cigarette butt Christmas tree in front of Korea Tobacco & Ginseng Corporation office in Seoul, South Korea, Monday, December 23, 2019. The environmental activist group called for a ban on the use of plastic for cigarette filters as part of efforts to protect the environment from toxic plastic pollution. (Photo by Ahn Young-joon/AP Photo)