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

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.

Pete Oxford / Glass Frog (Espadarana callistomma / centrolenidae). Captive. Chocó Region of northwest Ecuador.

Pete Oxford / Portrait of an Emerald Glass Frog (Espadarana / Centrolenella prosoblepon). Captive. Chocó Region of northwest Ecuador.

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

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

Edwin Giesbers / Ghost glass frog (Centrolenella ilex) portrait, Costa Rica

Michael D. Kern / Zoo Atlanta / White spotted glass frog {Cochranella albomaculata} portrait, captive, occurs Colombia, Costa Rica, Ecuador, Panama. Please credit Michael Kern / Zoo Atlanta.

Pete Oxford / Glass frog {Hyalinobatrachium sp} Amazonia, SE Ecuador

Pete Oxford / Glass frog with eggs visible through skin {Centrolenella sp} Ecuador, South America

Doug Wechsler / Pacific giant glass frog (Centrolenella geckoideum). NW Andes (2550m), Carchi Province, Ecuador, South America

Phil Savoie / Glass frog guarding its eggs (Centrolenella fleischmanni) Belize

Phil Savoie / Glass frog parent guarding eggs (Centrolenella fleischmanni) Belize

Phil Savoie / Glass frog on heliconia flower. (Centrolenella fleischmanni) Belize

Doug Wechsler / Glass frog in rainforest understorey, Ecuador

Christian Ziegler / Plantation Glass Frog (Hyalinobatrachiumácolymbiphyllum) is nearly transparent including the bones, only digestive tract is visible, Barro Colorado Island, Panama

Pete Oxford / Glass Frog (Hyalinobatrachium aureoguttatum) underside showing internal organs, native to South America

Pete Oxford / Glass Frog (Hyalinobatrachium aureoguttatum) underside showing internal organs, native to South America

Pete Oxford / Glass Frog (Hyalinobatrachium aureoguttatum) underside showing internal organs, native to South America

Pete Oxford / Glass Frog (Hyalinobatrachium aureoguttatum) pair, native to South America

Pete Oxford / Northern Glassfrog (Hyalinobatrachium fleischmanni) underside showing internal organs, northwest Ecuador

Heidi & Hans-Juergen Koch / Glass Frog (Cochranella antisthenesi) transparent skin shows body filled with eggs, very rare and fragile frog, native to Central and South America

Guy Edwardes / Emerald glass frog (Espadarana prosoblepon). Arenal, Costa Rica.

Nick Hawkins / Emerald Glass frog (Centrolenella proseblepan) underside view, from cloud forest in Choco region, Northwestern Ecuador.

Nick Hawkins / Emerald Glass frog (Centrolenella proseblepan) in cloud forest, Choco region, Northwestern Ecuador.

Nick Hawkins / Emerald glass frog (Centrolenella proseblepan) in cloud forest, Choco region, Northwestern Ecuador.

Morley Read / Resplendent cochran frog (Cochranella resplendens) on a leaf in the rainforest understory, Pastaza Province, Ecuador.

Morley Read / Resplendent cochran frog (Cochranella resplendens) on a leaf of a flowering Centropogon plant in the rainforest understory, Pastaza Province, Ecuador.

Morley Read / Resplendent cochran frog (Cochranella resplendens) on a leaf in the rainforest understory, with an ant walking past, Pastaza Province, Ecuador, April.

Morley Read / Resplendent cochran frog (Cochranella resplendens) on a leaf in the rainforest understory, Pastaza Province, Ecuador, April.

Morley Read / Glass frog (Centrolenidae) tadpoles developing in an egg mass, Cordillera del Condor, Zamora Chinchipe Province, Ecuador.

Morley Read / Glass frog (Centrolenidae) tadpoles developing in an egg mass, Cordillera del Condor, Zamora Chinchipe Province, Ecuador.

Morley Read / Glass frog (Centrolenidae) tadpoles developing in an egg mass, Cordillera del Condor, Zamora Chinchipe Province, Ecuador.

Morley Read / Slow motion clip of a Ghost glass frog (Sachatamia ilex) jumping, Santo Domingo Province, Ecuador, February 2018.

Morley Read / Close-up of a Ghost glass frog (Sachatamia ilex) showing pulsating eye display, used to startle predators, Samto Domingo Province, Ecuador, February 2018.

Morley Read / Glass frog (Espadarana) tadpoles developing in an egg mass, Cordillera del Condor, Zamora Chinchipe Province, Ecuador. Endangered.

Morley Read / Glass frog (Espadarana) tadpoles developing in an egg mass, Cordillera del Condor, Zamora Chinchipe Province, Ecuador. Endangered.

Morley Read / Glass frog (Espadarana) tadpoles developing in an egg mass, Cordillera del Condor, Zamora Chinchipe Province, Ecuador. Endangered.

Duncan Murrell / Sri Lanka whipping frog / Hour-glass tree-frog (Polypedates cruciger), Deniyaya, Sri Lanka. Endemic to Sri Lanka