Microtubules of fixed bovine pulmonary artery endothelial cells were labeled with our mouse monoclonal anti–a-tubulin antibody (Cat. No. A11126), detected with the biotin-XX–conjugated F(ab')2 fragment of goat anti–mouse IgG antibody (Cat. No. B11027) and visualized with Alexa Fluor® 488 streptavidin (Cat. No. S11223). The actin filaments were then labeled with orange-fluorescent Alexa Fluor® 568 phalloidin (Cat. No. A12380), and the cell was counterstained with blue-fluorescent Hoechst 33342 (Cat. No. H1399, H3570, H21492) to image the DNA, and red-fluorescent propidium iodide (Cat. No. P1304MP, P3566, P21493) to image the nucleolar RNA. The multiple-exposure image was acquired using bandpass filters appropriate for the Texas Red® dye, fluorescein, and DAPI.