Human whole blood was collected from a finger tip and diluted in PBS at 1:100. After staining with the AO/PI dyes, white blood cells (WBCs) were counted with the LUNA-FL fluorescence cell counter. Bright field and its corresponding fluorescence image are shown in the left and middle panel, respectively. Area enclosed by the white rectangle is shown in the right panel at high magnification. Note that cells containing nucleic acids (ie., WBCs) were counted and tagged with the green circle. A huge number of red blood cells (RBCs) and platelets seen in the bright field image were not counted by LUNA-FL. No dead WBC was observed in this field of view.