Think of it like this:

* Cells are the basic building blocks of life.

* Tissues are groups of similar cells working together.

* Organs are groups of different tissues working together to perform a specific function.

* Organ systems are groups of organs that work together to perform a larger, more complex function.

For example, the digestive system is made up of organs like the stomach, intestines, and liver. These organs work together to break down food, absorb nutrients, and eliminate waste.