cell wall

The cell wall is the tough, usually flexible but sometimes fairly rigid layer that surrounds some types of cells. It is located outside the cell membrane and provides these cells with structural support and protection, in addition to acting as a filtering mechanism. A major function of the cell wall is to act as a pressure vessel, preventing over-expansion when water enters the cell. Cell walls are found in plants, bacteria, fungi, algae, and some archaea. Animals and protozoa do not have cell walls.

The material in the cell wall varies between species, and can also differ depending on cell type and developmental stage.

The observation of cell wall was the first observation of cell structure at the microscopic level. It was done by Robert Hooke in 1665 using a simple light microscope by a transverse section cork.