In this video, we explore how the fingernail-sized Irukandji jellyfish can cause excruciating pain, organ failure, and even death with just a single sting.

This miraculous feat only occurs when the jellyfish has been harmed or is on the brink of starvation. In response, it winds back its biological clock to the time when it was a small larva.

Jellyfish can produce offspring both sexually ... for the comblike rows of tiny paddles they use to swim, they tend to be small, delicate, and hard to study. They come in an array of weird body ...