4. Fountain of Youth

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If scientists can figure this one out, it may mean a longer life for a lot of us. A species of jellyfish called turritopsis dohrnii ages normally just like any other jellyfish — until it reached adulthood, and then it does something amazing. It actually reverses the process and ages backwards until it becomes a baby again! As far as scientists have been able to figure out, these things can live forever!