Laser-scanning confocal microscopy of isolated Rh-123^low (A) and Rh-123^high (B) HSC. In each pair of images, the top frame was captured from transmitted light, while the bottom frame was a simultaneous fluorescent image. Identical magnifications (63X oil objective), illumination, and signal processing conditions were used to image the two cell types, assuring that the images are representative of the differential size and fluorescence intensity of the cells. Fluorescence images were inverted and pseudocolored so that increasing fluorescence intensity is indicated from blue to red. Note the relatively homogeneous cytoplasmic staining in the Rh-123^low cells compared with the intense bipolar perinuclear staining seen in Rh-123^high cells. The images are representative of 38 Rh-123^low cells and 28 Rh-123^high cells evaluated in two separate experiments.