Cnidaria

Simple, successful, and sometimes deadly, jellyfish can wreak havoc when they bloom, or they can inspire with their beauty.

Troublesome jellyfish blooms have prompted fears that jellyfish may come to dominate marine ecosystems thanks to humans, however, to some scientists this is premature and unfair.

The innocuously named sea walnut, a jellyfish, is actually an effective and stealthy predator, according to scientists.

It takes a lot of stinger-equipped tentacles.

The box jellyfish is pretty...pretty poisonous.

Clues to the a jellyfish's deadly sting may lead to an antidote.

Sea creatures stir the world's oceans.

A "jellyologist" explains the mysteries of large swarms of jellyfish that can cover hundreds of square miles of ocean.

Here's lookin' like you, babe. Jellyfish have many eyes that serve different purposes. One set works like ours.

In a region off the west coast of Africa, jellyfish are taking over. Similar scenarios play out around the globe.