The details of the microtubule network were visualized in a culture of RK13 epithelial cells (shown above) by employing immunofluorescence. The culture was labeled with mouse anti-alpha-tubulin followed by a secondary antibody (goat anti-mouse IgG) conjugated to Alexa Fluor 488. TO-PRO-3 (pseudocolored red) was utilized as a nuclear counterstain. Images were recorded with a 60x oil immersion objective using a zoom factor of 3.0 and sequential scanning with the 488-nanometer spectral line of an argon-ion 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.