If you saw one of these growing on the sea floor, you would think it was an aqueous plant, no different from any other type of seaweed. You would be wrong. Although Caulerpa has a complex structure with parts that look like leaves and stems and roots, and although it can grow to be over three feet long, it is actually a single cell. Caulerpa has only a single cell wall, surrounding the whole organism from the root tips to leaves. Within, the liquid of the cell flows freely. Structural support comes from a series of microscopic rods and microtubules, taking over the function of cell walls in multi-cellular plants. Perhaps the most interesting thing about Caulerpa is what it teaches us about life and evolution. It shows us that complex life does not need to evolve along only the lines we expect. Life can often surprise us!