The PtK2 epithelial cell culture illustrated above was transfected with a chimeric EGFP plasmid vector that expresses a fluorescent fusion protein targeted at keratin intermediate filament networks. The specimen was also stained for mitochondria with MitoTracker Red CMXRos, and for the nucleus with the DNA-selective compound Hoechst 33342 (pseudocolored cyan). Images were recorded with a 60x oil immersion objective using a zoom factor of 3.0 and sequential scanning with the 405-nanometer spectral line of a blue diode laser, the 488-nanometer spectral line of an argon-ion laser, and the 543-nanometer line from a green helium-neon laser. During the processing stage, individual image channels were pseudocolored with RGB values corresponding to each of the fluorophore emission spectral profiles unless otherwise noted above.