Here’s where it gets weird: some organisms blur the line entirely. Slime molds are single cells that can merge into a giant, gooey blob that acts like a multicellular creature. They can solve mazes without a brain. (I can barely solve a maze on a paper napkin.)
And Volvox is a green algae that forms tiny, hollow balls made of hundreds of cells. Each cell is separate, but they link arms and spin together like a synchronized swimming team. Are they a colony or a single organism? Biologists still argue. It’s like arguing whether a group of friends counts as a single person. (No, Karen, it doesn’t.)