GPMV growth begins soon after irradiation, usually within the first 30 s. Generally, vesicles’ growth rates decrease soon after they were initiated; however, they do not reach a final size within 60 min (for an example over 500 min, see Electronic supplementary material, Fig. S1). The vesicle volume can be estimated by assuming a spherical vesicle, in which case, these results do not change significantly. These data have a 10% uncertainty due to errors in visual vesicle edge determination and variation in microscope focal plane height relative to the largest vesicle cross-sectional area