As each droplet (containing a cell) passes through an electrical field of two charged plates (one positive and one negative), cells can be separated based on computer-generated predetermined properties of those cells (size, positivity for fluorescence, stain, or other markers). Positively charged droplets containing the desired cells are deflected by the negatively charged plate and pass into a collecting chamber. In a similar fashion, negatively charged droplets containing the positively charged cells pass into another chamber. Cells can be sorted at the rate of about 5,000 per second with 98% purity. Some cell sorters can separate up to four populations, making this a very powerful technique to isolate specific cell types.