English: Cell-to-cell transmission of virus particles towards target cells following completion of assembly. A HEK293 cell generating MLV labeled with Gag-YFP (red) and expressing dynamin2-CFP (green) in contact with a noninfected target XC cell expressing mCAT1-CFP (green) was monitored using spinning disc confocal microscopy. The cell-cell contact was imaged over a period of 1 h and 35 min. A z-stack of red and green images was taken every 60 s and merged into a single file to generate a QuickTime video. The video represents first the “red/green” sequence followed by the “red only” to facilitate the detection of de novo assembly events. At the end of each sequence, a single image is presented to display the merged image of all frames of the time-lapse video. The video is played at 10 frames/s. The six labeled particles correspond to particles A–F in Figure 4A.