Merged fluorescence and transmitted light images of NIH-3T3 cells transfected with control pEGFP vector (shown) or pEGFP fused to the HRPT2 tumor suppressor gene product and seeded on glass cover slips in 12-well plates. Twenty-four hours after transfection, the cells were washed with PBS, fixed with 2% formaldehyde in PBS and then stained with Hoechst 33342 dye for visualization of the nuclei. Confocal images were collected after excitation of fluorochromes using a 405 nm diode laser for Hoechst dye and a 488 nm laser for GFP. Differential interference contrast images were collected simultaneously with the fluorescence images using the transmitted light detector. For details, see the article by Lin et al. on p. 183.