Lucas Bustamante / Two Limon glass frogs (Sachatamia ilex) sitting on plant, one above the other, Canande, Esmeraldas.

Phil Savoie / Reticulated glass frog (Hyalinobatrachium valerioi) La Selva Field Station, Costa Rica.

Lucas Bustamante / Coastal glassfrog (Cochranella litoralis) on leaf with eggs. San Lorenzo, Esmeraldas, Ecuador.

Nick Garbutt / Montane Glass Frog (Centrolenella ilex) inside curled leaf. Mid-altitude rainforest, Bosque de Paz, Pacific slope, Costa Rica, Central America.

Nick Garbutt / Emerald Glass Frog (Centrolenella proseblepan) on leaf. Mid-altitude rainforest, Bosque de Paz, Pacific slope, Costa Rica, Central America.

Alex Hyde / Yellow-flecked glassfrogs (Sachatamia albomaculata) mating pair, Osa Peninsula, Costa Rica

Alex Hyde / Yellow-flecked glassfrogs (Sachatamia albomaculata) mating pair, Osa Peninsula, Costa Rica

Alex Hyde / Spined glassfrog (Teratohyla spinosa) Central Caribbean foothills, Costa Rica.

Edwin Giesbers / Reticulated glass frog (Hyalinobatrachium valerioi) captive, occurs in Colombia, Costa Rica, Ecuador, and Panama

Enrique Lopez-Tapia / Ship navigating the Huangpu River, Shanghai, China, September 2009. All non-editorial uses must be cleared individually.

Enrique Lopez-Tapia / Tjibaou Cultural Center designed by Renzo Piano. The building is designed to be integrated with the surrounding forest. Noumea, New Caledonia, September 2008.

Enrique Lopez-Tapia / A child sitting by wall with empty glass bottles, in the small village of Khumnu. Annapurna Sanctuary, central Nepal, November 2011.

Pal Hermansen / Silhouette of a Blue tit (Cyanistes / Parus caeruleus) seen through the windscreen of an old car, Bastnas, Sweden, December. Winner of the Fritz Polking Prize at the GDT competition 2013 and winner of...

Floris van Breugel / Glass beach at sunset - a former dump site, in which the glass has now become pebbles of sea glass. MacKerricher State Park. California. USA. January 2013

Visuals Unlimited / Emerald Glass Frog (Centrolenella prosoblepon), sitting within leaf tunnel, Costa Rica.

Niall Benvie,Niall Benvie / Common Frog (Rana temporaria) at surface, against white background. Scotland, UK, July.

Michael Pitts / Mike de Gruy, underwater camerman, in Remora submersible, Mediterranean

Gavin Hellier / People commuting through glass walled passageway in modern building, Berlin, Germany, 2009. No release available.

Paul D Stewart / Photomontage of living gecko feet showing a variety of forms. Gecko feet employ very small subdivided filaments to bond with their substrates at the molecular level using Van Der Waals' forces. Every...

David Shale / Male and Female glass shrimps on Glass sponge (Hexactinellida) from coral seamount, SW Indian Ridge, Indian Ocean, December 2011

Yves Lanceau / Domestic cat, brown tabby, head portrait, drinking milk from a glass.

Doc White / Girl in aquarium watching Beluga / White Whale (Delphinapterus leucas) in aquarium. Captive. Model released.

Paul Hobson / Robin (Erithacus rubecula) perched in broken window, UK, February

Juergen Freund / Mermaid's wineglass algae (Acetabularia calyculus) Batangas, Philippines.

John Cancalosi / Quartz (SiO2, silicon dioxide), the most common mineral on earth, used in making glass and other industrial uses.

Pete Oxford / Glass Frog (Espadarana callistomma / centrolenidae). Captive. Choc??gion of northwest Ecuador.

Pete Oxford / Portrait of an Emerald Glass Frog (Espadarana / Centrolenella prosoblepon). Captive. Choc??gion of northwest Ecuador.

Alex Hyde / Madagascar reed frog {Heterixalus madagascariensis} underside viewed through glass, Masoala Peninsula National Park, north east Madagascar.

Alex Hyde / Close-up of the underside of foot of Leaf-tailed gecko {Uroplatus sikorae} as it walks on vertical glass. The finely divided setae on the toe pads stick the gecko to the smooth surface through van der...

Philippe Clement / Lightning during thunderstorm above petrochemical industry seen through magnifying glass held against illuminated globe of the earth Digital composite

Michael D. Kern / Zoo Atlanta / White-spotted leaf frog (Cochranella albomaculata) captive, from Central America. Please credit Michael Kern / Zoo Atlanta.

Edwin Giesbers / Green lacewing (Chrysopa septempunctata) with reflection on glass, Menorca, Balearic Islands, Spain, Europe

Stephen Dalton / Muscid fly (Muscidae) on glass, viewed from under the glass showing feet, UK, controlled conditions

Stephen Dalton / Gecko (Tarentola sp) close up of feet gripping glass, controlled conditions

Wild Wonders of Europe / Lesniewski / European glass lizard (Ophisaurus apodus) Bagerova Steppe, Kerch Peninsula, Crimea, Ukraine, July 2009

Wild Wonders of Europe / Lesniew / European glass lizard (Ophisaurus apodus) portrait, Bagerova Steppe, Kerch Peninsula, Crimea, Ukraine, July 2009. WWE BOOK

Wild Wonders of Europe / Ziegler / European glass lizard (Pseudopus apodus) portrait, Western Peloponnesee, The Peloponnese, Greece, May 2009

Wild Wonders of Europe / Ziegler / European glass lizard (Pseudopus apodus) portrait, Western Peloponnesee, The Peloponnese, Greece, May 2009

Wild Wonders of Europe / Ziegler / European glass lizard (Pseudopus apodus) Western Peloponnesee, The Peloponnese, Greece, May 2009

Steven Kazlowski / Polar bear (Ursus maritimus) looking through window of a tundra buggy, with paws against the glass, 1002 coastal plain of the Arctic National Wildlife Refuge, Alaska, October 2005

Steven Kazlowski / Polar bear (Ursus maritimus) trying to bite window of a tundra buggy, with paws against the glass, 1002 coastal plain of the Arctic National Wildlife Refuge, Alaska, October 2005

David Shale / Glass squid {Teuthowenia megalops}, Mid-Atlantic Ridge, North Atlantic Ocean

David Shale / Piglet squid {Helicocranchia sp} from between 500 and 200m, Mid-Atlantic Ridge, North Atlantic Ocean

Laurent Geslin / Common bluebottle {Calliphora vomitoria} on window pane, UK

Igor Shpilenok / Kamchatka brown bear (Ursus arctos beringianus) at the 'Stained glass window', Valley of the Geysers, Kronotsky Zapovednik, Kamchatka, Far East Russia

Igor Shpilenok / Kamchatka brown bear (Ursus arctos beringianus) at the "Stained glass window" in the Valley of the Geysers, Kronotsky Zapovednik, Kamchatka, Far East Russia

David Shale / Deep sea Glass squid {Cranchia sp} from Mid-Atlantic Ridge