Jellyfish are multicellular organisms. They are actually made up of many different types of cells that work together to form tissues, organs, and organ systems.

Here's why you might think they are single-celled:

* Simple Appearance: Jellyfish have a relatively simple body structure compared to many other animals.

* No Bones or Complex Organs: They lack the complex internal structures, like bones and a brain, found in many other animals.

But despite their appearance, jellyfish are surprisingly complex creatures! They have specialized cells for things like digestion, movement, and even sensing their environment.