Only organisms classified as plants are made up of plant cells.

Here's why:

* Plant cells have unique features that distinguish them from animal cells, such as:

* Cell wall: A rigid outer layer that provides structural support.

* Chloroplasts: Organelles that contain chlorophyll for photosynthesis.

* Large central vacuole: A storage compartment for water and other substances.

* Other organisms (like animals, fungi, bacteria, etc.) are made up of different types of cells with different structures and functions.

So, if an organism is made up of cells with cell walls, chloroplasts, and large central vacuoles, then it's a plant!