Abstract: The present invention allows detection of specific cell types based on chemical and functional characteristics of the cells. The invention can discriminate even between cells that are very similar; for example, the invention can discriminate between fetal and maternal red blood cells. The invention can also selectively alter certain cells; for example, by lysing cells of one type while leaving cells of another type unaltered. The invention has numerous applications. For example, the invention allows separation of fetal cells from maternal cells in maternal blood, allowing for fetal genetic screening without many of the drawbacks of current fetal cell acquisition techniques.