Hydra has these unique stem cells that are in a continuous state of regeneration and recovery and seem to hold the code and key to biological immortality. Every 20 days, hydra renews totally into a new organism. It doesn't age or die; one can smash it into a pulp, cut it into tiny pieces, and mix them up, but a new hydra will grow out of it. This makes it ideal for studies in healing and ageing for regenerative research. These tiny creatures hold the answers to the biggest questions about life.