Here's a breakdown:

* Cells are the basic building blocks of life.

* Tissues are groups of similar cells that work together to perform a specific function.

* Organs are structures made up of different tissues that work together to perform a more complex function.

* Organ systems are groups of organs that work together to carry out major bodily functions.

* Organisms are complete living beings made up of multiple organ systems that work together to sustain life.

For example, the digestive system (made up of organs like the stomach, intestines, etc.) works with the circulatory system (heart, blood vessels) to get nutrients to the body's cells. Together, these organ systems contribute to the overall function and survival of the organism.