A team of Russian scientists in Antarctica has found an ancient lake buried under more than three kilometres of ice.
The lake – Lake Vostok – has been sealed off from the rest of the world for at least 15 million years.
Scientists think the lake may contain tiny organisms, like bacteria, which are not found anywhere else on earth.
If the organisms exist in the lake, it would be because they have been able to adapt to living in the darkness, saltiness and extreme cold of the hidden lake. In that case, they would likely have developed special features that no other organisms on earth have.