D71A dimers continually form and disintegrate dynamically. A typical video sequence (recorded and shown at a 33-ms resolution) showing three diffusing D71A(-AlexaFP) molecules and their trajectories (Video 1). Two molecules (green and red trajectories) first became colocalized in video frame 3 (67 ms), diffused together for 3 video frames (100 ms, see the trajectories; colocalization 1), and then separated. After diffusing as monomers for 133 ms, one of the two molecules (dark blue trajectory) became colocalized with a third molecule (pink trajectory) for 133 ms (colocalization 2), then separated.