Scientists unlock how glass frogs turn transparentbr br A frog that turns itself mostly transparent while sleeping may hold clues for understanding blood clotting in humans.br br Scientists have long known about the glass frog but did not understand how it made itself see-through.br br Now research has discovered that it is able to pool blood in its body without being negatively affected by clots.br br The findings could advance medical understanding of dangerous blood clotting - a common serious condition.br br The glass frog - which is about the size of a marshmallow - spends its days sleeping on bright green leaves in the Tropics.br br In order to escape the attention of predators, the creature turns itself up to 61 transparent, disguising itself on the leaf.