A method whereby one or more fluorescent dyes are used to bind and stain nucleic acids in certain blood cells, such as, for example, white blood cells, nucleated red blood cells, and reticulocytes, and to induce fluorescent emissions upon excitation of photons from a given source of light, such as, for example, a laser, at an appropriate wavelength. More particularly, this invention provides a method whereby a fluorescent trigger is used in a data collection step for collecting events that emit strong fluorescence, in order to separate white blood cells and nucleated red blood cells from red blood cells and platelets without the need for using a lysing agent.