Solvin Zankl / A Costa Rican researcher monitors the temperature in the developing sea turtle nests at Ostional beach, Costa Rica, November 2009. ^^^ Sea turtles have, like many other reptiles, temperature-dependent...

Juan Manuel Borrero / Egg-shaped sculpture balanced on roof and refelected in water at Salvador Dali's House-Museum. Port Lligat, Cap de Creus Natural Park, Gerona, Catalonia, Spain. March 2009.

Jack Dykinga / Weathered and eroded monzogranite boulders balanced precariously, sunset, Joshua Tree National Park, Mojave Desert, California, USA

Solvin Zankl / King penguin {Aptenodytes patagonicus} egg balanced on feet, Falkland Islands.

Claus Meyer / Tree Frog (Hyla sp) balanced on fern fiddlehead, Atlantic Forest, Brazil

Mitsuaki Iwago / King Penguin (Aptenodytes patagonicus) adult attends to its single egg balanced on its feet, South Georgia Island

Alex Mustard / 2020VISION / Pair of Reticulated dragonets (Callionymus reticulatus) spawning. The larger male is carrying the female up into the water column, balanced on his pectoral fin, the males breed only once in their life...

Alex Mustard / 2020VISION / Pair of Reticulated dragonets (Callionymus reticulatus) spawning - the larger male is carrying the female up into the water column, balanced on his pectoral fin, the males breed only once in their lif...

Jack Dykinga / Brilliant storm sunset over the boulders at 'Balanced Rock' illuminating the sky over the Salt Valley Wash, Utah, USA

Jack Dykinga / Storm clouds over Balanced Rock, Arches National Park in sunset light, Utah, USA

Jack Dykinga / Broken fossilized tree sections balanced on clay pedestals in sunset light, Petrified Forest National Park, Arizona, USA

Chris Gomersall / 2020VISION / Two Sea Life Surveys wildlife guides and border terrier dog in an inflatable boat, at the Cairns of Coll, Inner Hebrides, Scotland, UK, July 2011

Bryan and Cherry Alexander / Sculptural iceberg with a large chunk of ice balanced, Fish Islands, Antarctica, February 2009.

Bryan and Cherry Alexander / Sculptural iceberg with a large chunk of ice balanced, Fish Islands, Antarctica, February 2009.

Ingo Arndt / King Penguin (Aptenodytes patagonicus) adjusting egg balanced on its feet, King Edward Point, South Georgia Island

Ingo Arndt / King Penguin (Aptenodytes patagonicus) incubating egg balanced on its feet, King Edward Point, South Georgia Island

Peter Cairns / Pine Marten (Martes martes) balanced on branch. Cairngorms National Park, Scotland, August.

Solvin Zankl / A Costa Rican researcher monitors the temperature in the developing Olive Ridley sea turtle nests at Ostional beach, Costa Rica, November 2009. ^^^ Sea turtles have, like many other reptiles, temperat...

Stephen Dalton / Black rat (Rattus rattus) balanced on wire fencing at night, controlled conditions

Rob Tilley / Moon rising over balanced rock, Arches NP, Utah, USA, January 2008

Rob Tilley / Moon rising over balanced rock, Arches NP, Utah, USA, January 2008

Rob Tilley / Moon rising over balanced rock, Arches NP, Utah, USA, January 2008

Juan Manuel Borrero / Egg-shaped sculpture balanced on roof at Salvador Dali's House-Museum. Port Lligat, Cap de Creus Natural Park, Gerona, Catalonia, Spain. March 2009.

Pete Oxford / White fronted brown lemur (Lemur fulvus albifrons) male balanced between tree trunk and branch, Nosy Mangabe Island Reserve, Madagascar

Wild Wonders of Europe / Ruiz / Autumn leaf balanced on small twigs, Krasna Lipa, Ceske Svycarsko / Bohemian Switzerland National Park, Czech Republic, September 2008

Andy Rouse / King penguin (Aptenodytes patagonicus) adult walking with chick balanced on feet, Falkland Islands

Steven David Miller / Little Corella (Cacatua sanguinea gymnopis) pair balanced on branch, drinking from creek, Cooper Creek, Innamincka Regional Reserve, South Australia, July

Kirkendall-Spring / A balanced rock near the Tower of Babel in Arches National Park, Utah, USA.

Tim Fitzharris / Utah Juniper (Juniperus osteosperma) and Balanced Rock, Arches National Park, Utah

Tim Fitzharris / Moon over Balanced Rock, Arches National Park, Utah

Tim Fitzharris / La Sal Mountains and Balanced Rock, Arches National Park, Utah

Rob Tilley / Balanced Rock, Arches NP, Utah, USA

Rob Tilley / Balanced Rock, Arches NP, Utah, USA

Rob Tilley / Moonrise over Balanced Rock, Arches NP, UT, USA

Rob Tilley / Moonrise over Balanced Rock, Arches NP, Utah, USA

Tim Fitzharris / El Capitan and Balanced Rock, Guadalupe Mountains National Park, Texas

Tim Fitzharris / El Capitan and Balanced Rock, Guadalupe Mountains National Park, Texas

David Noton / Balanced Rock, Arches National Park, Utah, USA

David Noton / Balanced Rock, Arches National Park, Utah, USA

Tim Fitzharris / Balanced rock, Guadalupe Mountains, Texas

Tim Fitzharris / Balanced rocks, Guadalupe Mountain National Park, Texas

David Noton / Balanced rock, snow covered La Sal mountains in background, Arches NP, Utah, USA

Terry Andrewartha / Close-up of egg balanced on feet of King penguin (Aptenodytes patagoni) South Georgia

Solvin Zankl / King penguin {Aptenodytes patagonicus} egg balanced on parent bird's feet, Falkland Islands.

Solvin Zankl / King penguin{Aptenodytes patagonicus} adjusting egg balanced on its feet, Falkland Islands.

Mark Taylor / Balanced sandstone rocks locally known as 'Goblins'. Utah, USA.

Tim Fitzharris / Balanced rock under cloudy skies, Arches National Park, Utah

Tim Fitzharris / Balanced rock in the Grapevine Mountains, Big Bend National Park, Texas

David Noton / Juniper tree growing in Balanced Rock Arches National Park, Utah, USA, North America

Pete Cairns / Balanced rock sandstone formation in Arches NP, Utah, USA

Gavin Hellier / 'Balanced Rock' and the La Sal mountains, Arches NP, Utah, USA

Ingo Arndt / King Penguin (Aptenodytes patagonicus) incubating egg balanced on its feet, King Edward Point, South Georgia Island

Tom Vezo / Brunnich's guillemot {Uria lomvia} egg balanced on cliff ledge, St Paul Island, Pribilof Islands, Alaska, USA