English: Formation of clathrin-coated structures on the free surface of Swiss 3T3 cells. Time-series images of clathrin assemblies at the plasma membrane on the top of a Swiss 3T3 fibroblast stably expressing clathrin LCa-DsRed imaged using spinning disk confocal microscopy at 5-s intervals and 100-ms exposure time. The video shows 68 frames (340 s). Notice that the mobility of the clathrin assemblies is in part due to overall movement of the cell; some structures are clathrin coats on mobile endosomes.