So turns out the "Hydrozoan Jellyfish" has the ability to manipulate it's cells to revert back to whatever age they please. They're the only known Immortal animal.
ALSO Scientists have found more ways to cloak things from visibility, including infrared. (as far as I know)

So soon we're all going to be invisible AND immortal.
cool, hm?

The world's only immortal animal | Yahoo! Green

Cloak of invisibility takes a step forward - Yahoo! News