Here's why:

* Tissue: A group of similar cells that work together to perform a specific function.

* Organ: A structure made up of two or more different types of tissues that work together to perform a complex function.

For example, the stomach is an organ. It contains muscle tissue (for churning), epithelial tissue (for lining), connective tissue (for support), and nervous tissue (for coordination). All these tissues work together to digest food.