Hydra is a genus of simple fresh-water animal possessing radial symmetry. They are multicellular organisms which are usually a few millimetres long and are best studied with a microscope, and can be found in most unpolluted fresh-water ponds, lakes, and streams in the temperate and tropical regions.

When the Greek hero Hercules sliced through one of the Lernaean Hydra's nine heads, two grew back in its place. This mythical creature's real life counterparts, a genus of tiny cylindrical animals known as Hydra, have equally impressive regenerative powers, prompting physicists to adapt a computer model to unlock these animals' secrets.

http://phys.org/…prowess.html