In the deep seas swims a creature with one of the most unbelievable abilities in the animal kingdom: Turritopsis dohrnii, better known as the immortal jellyfish. What makes it “immortal”? When facing injury, starvation, or even old age, this jellyfish doesn’t die—it reverts to its earliest life stage, essentially starting its life cycle over.
Instead of aging to death, the jellyfish undergoes a process called transdifferentiation, where its cells transform into different types to rejuvenate itself. It’s the only known animal capable of repeatedly reverting back to a polyp stage and beginning its life again.
While it’s not truly invincible—predators and disease can still kill it—this microscopic marvel represents a biological phenomenon that scientists are still striving to fully understand. It’s a real-life reset button, floating beneath the waves.