A431 cells labeled with probes for histones and the epidermal growth factor (EGF) receptor. Histones were detected with a mouse anti-histone antibody prelabeled using the Zenon® Alexa Fluor® 488 Mouse IgG_2a Labeling Kit (Cat. no. Z25102). EGF receptors on the cell surface were detected with a mouse anti–EGF receptor monoclonal IgG_2a antibody prelabeled using the Zenon® Alexa Fluor® 555 Mouse IgG_2a Labeling Kit (Cat. no. Z25105).