And we use a technique called Gram staining to basically differentiate between these two different types of bacterial cells. So we have Grampositive bacteria and Gram negative bacteria. So, Grampositive bacteria contain a very thick peptidogly cell wall, about four times as thick as the actual plasma membrane. And because of this relatively large thickness of the Peptidoglycan cell wall, when we actually stain our bacteria with some type of purple dye, that purple color remains within that cell because it cannot leave, it cannot leak out of our relatively thick Peptidoglycan wall. And so, under the microscope, when we actually take our bacteria, the Grampositive bacteria, and stain it with the purple dye, those bacterial cells will appear purple under the microscope. So Grampositive bacterial cells are cells that are characterized by thick cell wall.