Here's a breakdown of the levels of organization:

1. Cells: The basic, fundamental unit of life.

2. Tissues: Groups of similar cells working together to perform a specific function.

3. Organs: Structures made up of different tissues that work together for a common purpose.

4. Organ Systems: Groups of organs that cooperate to carry out major bodily functions.

5. Organism: A complete living being composed of all the organ systems working together.