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

* Cells are the basic unit of life, and while they can perform some functions on their own, they are much more effective when working together in a coordinated way.

* Organs are composed 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 life functions.

Examples of tissues:

* Muscle tissue: Made of cells that can contract, allowing for movement.

* Nervous tissue: Composed of nerve cells (neurons) that transmit signals throughout the body.

* Connective tissue: Provides support and structure, such as bone and cartilage.

* Epithelial tissue: Covers surfaces of the body, such as skin and the lining of internal organs.