And, well, why are they called glass frogs? First, I should note that there are +/- 149 species of glass frogs known, with 14 of those found in Costa Rica, so there are a lot of various glass frogs out there. And for the most part they are pretty darn see-through, like glass. You really can just look right through the things and see all the internal organs and whatnot. Here is a photo taken with a front lighting that shows this.