Just imagine if you could rewind time and become young again whenever life got tough. For Turritopsis dohrnii, a tiny jellyfish, this is actually possible. Known as the "immortal jellyfish," it has the remarkable ability to revert to an earlier stage of its life cycle, potentially defying the normal aging process.

The life cycle of Turritopsis dohrnii is similar to that of any other jellyfish. It starts off as a fertilized egg, which then turns into a larval form known as a planula. The planula will then attach itself to a surface and develop from there into a polyp, where the polyps become larger colonies and feed on nutrients. Over a certain time period, one of the polyps develops to become a bud, matures further to become the ephyra-the juvenile jellyfish-and further matures into the fully mature medusa, capable of sexual reproduction.

But what makes Turritopsis dohrnii remarkable is its ability to reverse its life cycle when environmental stress, such as starvation or injury, occurs. Rather than aging and dying, it transforms back into the polyp stage through a process called transdifferentiation, which lets it evade the usual process of aging and start a new life cycle. It's a bit like the butterfly reversing to become a caterpillar.

While this capacity puts the jellyfish in a singular position, it is not immortally biologically. This creature can be eaten by its predators or suffer from disease. However, Turritopsis dohrnii opens a window into the theoretical concept of biological immortality. This makes science curious about aging and regeneration.

Among the animals in the world, the "immortal" jellyfish is the most outstanding manifestation of nature's capability to manipulate the laws of life and death.