Don’t underestimate a flatworm! Planarians, the regenerating rogues of the aquatic world, can be rebuilt entirely from a single stem cell. We’ve known for a while that flatworms can regrow severed heads (chop one in half, and voilà—two planarians wriggle off.)

Now, recent research has shone a light on exactly how they do it. See, while humans lose their pluripotent cells (cells that can become any cell type) after early development, flatworms keep these cells for life, enabling constant regeneration. Amazingly, scientists can even manipulate them to grow multiple heads, like Hydra from Greek mythology, but on a much smaller scale.

Beyond cool science class fodder, Planarians are paving the way for breakthroughs in regenerative medicine.