This frog hides its blood to disappear

How does a living creature turn into a piece of glass? The glass frog vanishes by hiding its own blood inside its liver.

While most animals are opaque, this frog’s underside is completely translucent. Looking at one is like looking through a telescope; you can watch its heart beat, see food move through its gut, and track its bones.

Normally, the red blood cells circulating through its body would give it away to predators. To solve this, the frog packs nearly 90% of its red blood cells into its liver while it sleeps.

The liver has a mirrored surface that reflects the light, masking the red color. This turns the frog’s body into a living window that blends perfectly with the leaf it sits on.

Humans would develop massive, fatal blood lumps if we tried this. The frog carries a chemical signature that prevents clotting even when its blood is packed tight in one organ. When the frog wakes up, the blood cells simply flood back into its veins, and it turns solid once again.

Curiously, these frogs aren't born clear; they only develop this 'disappearing act' as they mature into adults.