Turritopsis nutricula may be the world’s only “immortal” creature.
Jellyfish usually die after propagating but Turritopsis reverts to a sexually immature stage after reaching adulthood and is capable of rejuvenating itself.
The 4-5mm diameter creature, technically known as a hydrozoan, is the only known animal that is capable of reverting to its juvenile polyp state.
Theoretically, this cycle can repeat indefinitely, rendering it potentially immortal.