1. Humans: We are multicellular organisms, meaning we are made up of trillions of cells that work together to form tissues, organs, and organ systems.

2. Trees: Plants, like trees, are also multicellular organisms. Their cells contain chloroplasts, which allow them to perform photosynthesis and create their own food.

3. Bacteria: Though single-celled, bacteria are living organisms made up of a single cell. They are incredibly diverse and play crucial roles in ecosystems, from decomposing matter to producing oxygen.