The microtubule network and cell nuclei are revealed in this confocal image of gerbil lung fibroblasts stained with Alexa Fluor 555 (tubulin) and TO-PRO-3 (DNA). The cells were fixed with 3.7 percent paraformaldehyde, permeabilized with Triton X-100, blocked with 10 percent normal goat serum and treated with mouse anti-alpha-tubulin primary antibodies. Goat anti-mouse secondary antibodies conjugated to Alexa Fluor 555 were mixed with the nucleic acid stain. Images were recorded with a 60x oil immersion objective using a zoom factor of 2.0 and sequential scanning with the 543-nanometer line from a green helium-neon laser and the 633-nanometer line of a red helium-neon laser. During the processing stage, individual image channels were pseudocolored with RGB values corresponding to each of the fluorophore emission spectral profiles, with the exception of TO-PRO-3, which was pseudocolored cyan.