An expedition to the coastal rainforests of Ecuador has discovered transparent frogs, tiny geckos and snail-sucking snakes. The beating heart of this see-through frog can be clearly seen. Part of the ...

Glass frogs also have a unique circulatory system, with veins that are closer to the surface of the skin. This allows the oxygen-rich blood to be visible through the skin ...

Glass frogs have the rare ability to turn on and off their nearly transparent appearance, researchers report Thursday in the journal Science. Ernesto Benavides/Getty Images Now you see them, now you ...