Fern fiddleheads at Valley Falls Park in Vernon, Connecticut (© Holcy/Getty Images)(Bing United States)

Fern fiddleheads at Valley Falls Park in Vernon, Connecticut (© Holcy/Getty Images)(Bing United States)

The Pyramids of Meroë in Sudan (© Andrew McConnell/Alamy)(Bing United States)

The Pyramids of Meroë in Sudan (© Andrew McConnell/Alamy)(Bing United States)

The Brooklyn Bridge, New York (© Inge Johnsson/age fotostock)(Bing United States)

The Brooklyn Bridge, New York (© Inge Johnsson/age fotostock)(Bing United States)

White-throated dipper at Tufa Dam, on the River Lathkill in Derbyshire, England (© Ben Hall/Minden Pictures)(Bing United States)

White-throated dipper at Tufa Dam, on the River Lathkill in Derbyshire, England (© Ben Hall/Minden Pictures)(Bing United States)

Thunderstorms over Lake Powell, Arizona (© Babak Tafreshi/Getty Images)(Bing United States)

Thunderstorms over Lake Powell, Arizona (© Babak Tafreshi/Getty Images)(Bing United States)

Burchell's zebra stallion chasing a rival in Rietvlei Nature Reserve, South Africa (© Richard Du Toit/Minden Pictures)(Bing United States)

Burchell's zebra stallion chasing a rival in Rietvlei Nature Reserve, South Africa (© Richard Du Toit/Minden Pictures)(Bing United States)

US Air Force Thunderbirds at an airshow in Smyrna, Tennessee (© Jim Zuckerman/Alamy)(Bing United States)

US Air Force Thunderbirds at an airshow in Smyrna, Tennessee (© Jim Zuckerman/Alamy)(Bing United States)

Cyclist in Trondheim, Norway (© Jonas Froland/plainpicture)(Bing United States)

Cyclist in Trondheim, Norway (© Jonas Froland/plainpicture)(Bing United States)

Paläon Research and Experience Center, Schöningen, Germany (© WestEnd61/REX/Shutterstock)(Bing United States)

Paläon Research and Experience Center, Schöningen, Germany (© WestEnd61/REX/Shutterstock)(Bing United States)

Uinta ground squirrels at Tower Fall Campground in Yellowstone National Park, Wyoming (© Shin Yoshino/Minden Pictures)(Bing United States)

Uinta ground squirrels at Tower Fall Campground in Yellowstone National Park, Wyoming (© Shin Yoshino/Minden Pictures)(Bing United States)

Porthminster Beach and St. Ives, Cornwall, England (© Adam Burton/Minden Pictures)(Bing United States)

Porthminster Beach and St. Ives, Cornwall, England (© Adam Burton/Minden Pictures)(Bing United States)

Incense factory in Xinhui District, Jiangmen City, Guangdong Province, China (© Wallace Cheah/500px)(Bing United States)

Incense factory in Xinhui District, Jiangmen City, Guangdong Province, China (© Wallace Cheah/500px)(Bing United States)

Cheetah mother and her week-old cub, Maasai Mara National Reserve, Kenya (© Suzi Eszterhas/Minden Pictures)(Bing United States)

Cheetah mother and her week-old cub, Maasai Mara National Reserve, Kenya (© Suzi Eszterhas/Minden Pictures)(Bing United States)

Sandhill cranes over barley fields near the Alaska Range, Delta Junction, Alaska (© Yva Momatiuk and John Eastcott/Minden Pictures)(Bing United States)

Sandhill cranes over barley fields near the Alaska Range, Delta Junction, Alaska (© Yva Momatiuk and John Eastcott/Minden Pictures)(Bing United States)

Vernal Fall at Yosemite National Park, California (© Framepool)(Bing United States)

Vernal Fall at Yosemite National Park, California (© Framepool)(Bing United States)

A mountain goat in Glacier National Park, Montana (© Sumio Harada/Minden Pictures)(Bing United States)

A mountain goat in Glacier National Park, Montana (© Sumio Harada/Minden Pictures)(Bing United States)

Ward Charcoal Ovens State Historic Park in Nevada (© Royce's Nightscapes/500px)(Bing United States)

Ward Charcoal Ovens State Historic Park in Nevada (© Royce's Nightscapes/500px)(Bing United States)

A female wood duck and ducklings in Arapahoe County, Colorado (© Robert Harding/Alamy)(Bing United States)

A female wood duck and ducklings in Arapahoe County, Colorado (© Robert Harding/Alamy)(Bing United States)

Guoliang Tunnel in the Taihang Mountains in Henan Province, China (© View Stock/Offset)(Bing United States)

Guoliang Tunnel in the Taihang Mountains in Henan Province, China (© View Stock/Offset)(Bing United States)

Greyface moray eels in the Andaman Sea (© Reinhard Dirscherl/Aurora Photos)(Bing United States)

Greyface moray eels in the Andaman Sea (© Reinhard Dirscherl/Aurora Photos)(Bing United States)

The path to Morskie Oko, Tatra National Park, Poland (© Blake Parker/Tandem Still + Motion)(Bing United States)

The path to Morskie Oko, Tatra National Park, Poland (© Blake Parker/Tandem Still + Motion)(Bing United States)

Henequen agave, Yucatán Peninsula, Mexico (© Brian Overcast/Alamy)(Bing United States)

Henequen agave, Yucatán Peninsula, Mexico (© Brian Overcast/Alamy)(Bing United States)

Close-up of the nose of space shuttle Atlantis on exhibit at Kennedy Space Center, Florida (© Matthew Kuhns/Tandem Stills + Motion)(Bing United States)

Close-up of the nose of space shuttle Atlantis on exhibit at Kennedy Space Center, Florida (© Matthew Kuhns/Tandem Stills + Motion)(Bing United States)

Navagio Beach at Zakynthos, Greece (© Maciej Tomków/Nimia)(Bing United States)

Navagio Beach at Zakynthos, Greece (© Maciej Tomków/Nimia)(Bing United States)

Cleaning the elephant specimens at the Natural History Museum of Los Angeles County, California (© Brian Doben/Gallery Stock)(Bing United States)

Cleaning the elephant specimens at the Natural History Museum of Los Angeles County, California (© Brian Doben/Gallery Stock)(Bing United States)

Inside the Kibble Palace at Glasgow Botanic Gardens, Scotland (© Allan Baxter/Gallery Stock)(Bing United States)

Inside the Kibble Palace at Glasgow Botanic Gardens, Scotland (© Allan Baxter/Gallery Stock)(Bing United States)