The vitality of the cell sample is measured by staining the cells with calcein AM Once the counting is complete, the Cellometer software automatically reports the total number of counted cells that are calcein AM active, and the concentration of cells. Displayed above are the captured bright-field, captured fluorescent, and the counted fluorescent images from a whole blood sample. Only the white blood cells and platelets are stained with calcein AM Since red blood cells are not stained, they do not interfere with counting. In the counted fluorescent image, counted particles are outlined with a green circle. In this case only the platelets are counted whereas the white blood cells, outlined with a yellow circle, are excluded from counting based on their cell size.