To understand disease and develop new drugs, researchers often must begin by sorting the jumble of cell types in a living organism-tumor cells from normal cells, for instance. In some cases, a refrigerator-sized "fluorescence-activated cell sorter," or FACS, can do the job. These machines, however, are expensive ($250,000), tricky to operate and prone to contamination. Now a team at Caltech, led by applied physicist Stephen Quake, has built a "microFACS," reducing the complicated system of pumps, tubes and nozzles to micrometers-wide channels in a stamp-sized rubber chip.

Select from the choices above to read the entire article.