The oldest 'footprints' ever made on Earth by an animal have been discovered in Poland, in Eastern Europe.
The tracks were made by an unknown creature, which scientists think would have looked a bit like a crocodile, and lived 397 million years ago.
Scientists are really excited about the discovery, because it shows animals were walking on Earth millions of years earlier than they thought.
It's hoped the tracks can teach them more about how animals have developed.
The tracks were found on rocks in a quarry in southeast Poland.
They are so detailed that scientists can even make out dents made by the creatures' toes when walking.
When the animals were alive the quarry would have been a muddy, tropical beach.
Scientists can make out 'toes' on the ancient footprints
Scientists think these crocodile-like animals were some of the first creatures that adapted to live on dry land.
Little is known about how creatures developed from living underwater to walking on land, and it's hoped these footprints will teach scientists more about this bit of evolution.
According to the theory of evolution, today's animals got here after millions of years of growing and changing.
The research was published in a science magazine called Nature.