Giant vesicles (GVs) comprising zwitterionic and anionic phospholipids (DOPC and POPG, respectively) at a molar ratio of 90:10 formed a sparse network of aggregates that dissociated into isolated GVs reversibly depending on the pH of the dispersion (pH range, 7.0-2.5). This reversibility was due to the fluctuations in the composition of as-grown GVs.