Nuclear histone proteins were targeted in the culture of 3T3 cells presented above with mouse anti-histone (pan) monoclonal antibodies, which were imaged with goat anti-mouse Fab fragments conjugated to Alexa Fluor 568 (labeling the nucleus). The specimen was simultaneously labeled for peroxisomes with Alexa Fluor 488 conjugated to goat secondary antibodies that target rabbit anti-PMP 70 (peroxisomal membrane protein 70). 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, as well as 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.