Cherry blossoms at the Japanese Tea Garden in Golden Gate Park, San Francisco, California (© luisascanio/iStock/Getty Images)

Burchell's zebra stallions, Rietvlei Nature Reserve, South Africa (© Richard Du Toit/Minden Pictures)

Poster for Teacher Appreciation Week by 12-year-old Caroline Holt, 7th-grade student at the Bush School, Seattle, Washington (© Caroline Holt/Eugenia Chang)

Grey seal hitching itself over the beach at Donna Nook, North Lincolnshire, England (© Frederic Desmette/Minden Pictures)

The Great Pyramid of Cholula, in Cholula, Puebla, Mexico (© mauritius images GmbH/Alamy)

Norcross Brook and wetlands near Moosehead Lake in Piscataquis County, Maine (© Aaron Black-Schmidt/Tandem Stills + Motion)

Black-tailed godwits, Netherlands (© Edward van Altena/Minden Pictures)

Sea otter mother and newborn pup, Monterey Bay, California (© Suzi Eszterhas/Minden Pictures)

The Hōkūle'a, a traditional Hawaiian voyaging canoe, departs for a 3-year voyage from Honolulu, Hawaii, on May 17, 2014 (© Reuters/Alamy)

Grinnell Lake, Glacier National Park, Montana (© Pung/Shutterstock)

A view across the River Shannon in Limerick, County Limerick, Ireland (© Piotr Machowczyk/Shutterstock)

Shikisai no Oka flower gardens in Biei, Japan (© Tanya Jones/Shutterstock)

Amazon rainforest with morning fog near Alta Floresta, Mato Grosso, Brazil (© Pulsar Imagens/Alamy)

Telescopes and star trails at Paranal Observatory, Atacama Desert, Chile (© Matteo Omied/Alamy)

Aerial view of El Peñón de Guatapé, Guatapé, Antioquia, Colombia (© Amazing Aerial Agency/Offset by Shutterstock)

Ålesund, Norway (© AWL Images/Offset by Shutterstock)

Centre Pompidou Málaga in Málaga, Spain (© Wim Wiskerke/Alamy)

Fallen rhododendron petals line a trail through Pisgah National Forest, North Carolina (© aheflin/Getty Images Plus)

A bee dives into a lotus flower at Kenilworth Park and Aquatic Gardens in Washington, DC (© Linda Davidson/The Washington Post via Getty Images)

Whooping cranes taking off during spring migration in South Dakota (© Gerrit Vyn/Minden Pictures)

The medieval walled town in Tossa de Mar, Catalonia, Spain (© dleiva/Alamy)

The renovated Rose Main Reading Room, New York Public Library Main Branch, New York City (© Sascha Kilmer/Getty Images)

The Infinite Bridge in Aarhus, Denmark (© Kosmaj/Shutterstock)

Sperm whale off the coast of Roseau, Dominica, in the Caribbean Sea (© Tony Wu/Minden Pictures)

The total lunar eclipse of April 4, 2015, photographed over Monument Valley, Utah (© Alan Dyer/Alamy)

'I Can Hear It,' an installation by artist Ivars Drulle on the beach by the villages of Middelkerke and Westende, Belgium (© Arterra Picture Library/Alamy)

Robin's nest with a brown-headed cowbird egg (© Edward Kinsman/Science Photo Library)

Alley and bamboo grove in Wuhou Temple, Chengdu, Sichuan province, China (© Eastimages/Getty Images)

California sea lion in a forest of giant kelp near the Channel Islands of California (© Nature Picture Library/Alamy)

Military Women's Memorial, located at the gateway to Arlington National Cemetery, Virginia (© Brycia James/Getty Images)