For Siblings Day, lion cubs wrestle in Samburu National Park, Kenya (© Mark C. Ross/Getty Images)

Books by Hans Christian Andersen (© radiokafka/Adobe Stock)

Milky way over the Bisti/De-Na-Zin Wilderness in New Mexico (© Cory Marshall/Tandem Stills + Motion)

For Earth Month, a symmetrical forest known as a Nelder Plot (© Rachid Dahnoun/Tandem Stills + Motion)

Blossoming cherry trees at a tea plantation in Longyan, China (© VCG/Getty Images)

Blue quandongs and colourful leaves on subtropical rainforest floor, Currumbin Creek Valley (© Auscape/UIG via Getty Images)

For International Beaver Day a beaver swimming in Grand Teton National Park (© Charlie Hamilton James/Getty Images)

The National Wallace Monument overlooking Stirling in Scotland (© Elena Korchenko/age fotostock)

Bioluminescent algae along the shores of the Matsu Islands off the coast of Taiwan (© Wan Ru Chen/Getty Images)

Alpine eucalypt bark in Tasmania (© Australian Scenics/Getty Images)

The Mount Washington Observatory in New Hampshire (© Mike Theiss/Getty Images)

Vinyl records in Rosmalen, The Netherlands (© DutchScenery/Shutterstock)

Path to San Juan de Gaztelugatxe, Basque Country, Spain, for the 'Game of Thrones' premiere (© Anton Petrus/Moment/Getty Images)

A woman looks at Yayoi Kusama's 'With All My Love for The Tulips, I Pray Forever (2011)' (© Timothy A. Clary/Getty Images)

石楠花丛中的雄狍 (© wonderful-Earth.net/Alamy Stock Photo)

Hope Valley, Peak District, England (© Daniel_Kay/Getty Images Plus)

Dubai Miracle Garden, United Arab Emirates (© Amazing Aerial/Offset)

Paepalanthus flowers at sunset, Chapada dos Veadeiros National Park, Brazil (© Marcio Cabral/Getty Images)

Autumn colours in New England, New South Wales (© ILYA GENKIN/Alamy Stock Photo)

A rabbit in the grass (© wisan224/Getty Images Plus)

Laysan albatross chick on Midway Atoll, Hawaiian Leeward Islands (© Jaymi Heimbuch/Minden Pictures)

At Casa Batlló for Saint Jordi’s Day in Barcelona, Spain (© Jon Arnold Images Ltd/Alamy)

The Quinault Rainforest in Olympic National Park, Washington (© Jason Savage/Tandem Stills + Motion)

Australian National War Memorial, Canberra (© craighind/iStock Editorial/Getty Images Plus)

Hummingbird near blooming aloe vera in Laguna Beach, California (© Aurora Photos/Offset)

Dawn in the vineyards near Margaret River, Australia (© Nick Rains/Corbis NX/Getty Images)

Prairie and pinnacles near Castle Trail in Badlands National Park, South Dakota (© Danita Delimont/Getty Images)

Newborn brown-throated sloth with mother, Sloth Sanctuary of Costa Rica (© Suzi Eszterhas/Minden Pictures)

Louis Armstrong performs with bandmates in Vienna, Austria, on February 22, 1959 (© Franz Hubmann/Getty Images)

Wisteria blooms at Kawachi Fuji Gardens in Kitakyushu, Japan (© Wibowo Rusli/Alamy)