A tadpole is the swimming, fishlike baby form of a frog or toad. When frogs lay their eggs in ponds or streams, tiny tadpoles hatch out and look nothing like their parents. They have round heads, long tails for swimming, and gills for breathing underwater, just like fish do.

Over several weeks or months, something remarkable happens: the tadpole gradually transforms into an adult frog through a process called metamorphosis. Back legs sprout first, then front legs. The tail slowly shrinks and disappears. Lungs develop so the tadpole can breathe air. Its mouth widens so it can catch insects instead of nibbling algae. Eventually, a creature that once could only live underwater becomes an amphibian that spends much of its time on land.

If you've ever caught tadpoles in a jar or bucket to watch them up close, and then returned them to where you found them, you've witnessed one of nature's most dramatic transformations.