Time-lapse microscopy analysis of N4-Dendra2 uptake by N1-mCherry-expressing cells. A431D cells expressing N1-mCherry (red, endosomal localization) were co-cultured with A431D cells expressing N4-Dendra2 (green, plasma membrane localization). Cells were imaged on the second day after plating. Green and red images were taken simultaneously using an image splitter in 1 min intervals using halogen light that minimized phototoxicity and photobleaching and are shown at 2 images per second. White arrows indicate green fluorescence moving from the plasma membrane of N4 cells into N1 cells. Yellow color visualizes co-localization of green and red signals.