A group of different tissues working together is called an organ.

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 made up of different tissues that work together to carry out a more complex function.

* Organ Systems are groups of organs that work together to perform a major bodily function.

For example, the stomach is an organ made up of muscle tissue, epithelial tissue, connective tissue, and nervous tissue. These tissues work together to digest food.