Layers of cells that are similar in structure and perform a certain function are called tissues.

Here's a breakdown:

* Cells: The basic building blocks of all living organisms.

* Tissues: Groups of similar cells that work together to perform a specific function.

* Organs: Structures made up of different tissues that work together to perform a more complex function.

* Organ systems: Groups of organs that work together to carry out major bodily functions.

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