On page 1210, Tibbe et al. describe a cell analysis system for simultaneously extracting a population of cells from a complex mixture, and positioning the cells for optical examination. The cell mixture (in this case whole blood) is stained with fluorescent dyes and antibody-coated iron particles, and placed in a tiny chamber containing specially positioned magnets. Cells that bind the antibodies move to the top of the chamber, and then align along magnetic lines deposited using lithographic techniques. Once positioned, this specific population of cells can be examined for fluorescence, placed in new buffers, or otherwise manipulated.