In order to visualize the microtubules present in the gerbil lung cells illustrated in the digital image above, a GeLu culture was immunofluorescently labeled with anti-tubulin mouse monoclonal primary antibodies followed by goat anti-mouse Fab fragments conjugated to Alexa Fluor 488. In addition, the cells were labeled for the cytoskeletal F-actin network with Alexa Fluor 546 (pseudocolored blue) conjugated to phalloidin, and for cell nuclei with TO-PRO-3. Images were recorded with a 60x oil immersion objective using a zoom factor of 2.5 and sequential scanning with the 488-nanometer spectral line of an argon-ion laser, 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 unless otherwise noted above.