"Caulerpa is a unique organism". "It's a member of the green algae, which are plants. Remarkably, it's a single cell that can grow to a length of six to twelve inches. It independently evolved a form that resembles the organs of land plants. A stolon runs along the surface that the cell is growing on and from the stolon arise leaf-like fronds, and root-like holdfasts, which anchor the cell and absorb phosphorus from the substrate. All of these structures are just one cell."
The structure of Caulerpa might be reflected in the RNA's present in various parts of the cell. (RNA's are the molecular products found when genes are expressed or "turned on.") For example, the frond part of the cell might show different RNA's from the holdfast part of the cell. When performed on Caulerpa, this type of analysis would also provide insights into the distributions of RNA's within single cells, a feat normally difficult to achieve because cells in multicellular organisms are so small.