A collection of two or more tissues that work together to perform a specific function is called an organ.

Here's a breakdown:

* Tissues: Groups of similar cells that perform a common function.

* Organ: A structure made up of different tissues that work together for a specific purpose.

Examples of organs:

* Heart: Made of muscle tissue (to pump blood), connective tissue (to provide structure), and nervous tissue (to regulate heart rate).

* Stomach: Composed of muscle tissue (to churn food), epithelial tissue (to line the stomach), and connective tissue (to provide support).

* Brain: Consists of nervous tissue (for processing information) and connective tissue (to support and protect neurons).

Let me know if you'd like to know more about tissues, organs, or organ systems!