Incubation of a cell-sized lipid membrane vesicle (giant vesicle, GV) in a diluted aqueous solution of neutral phosphate buffer salts or glucose transformed the GV to an oligovesicular vesicle (OVV) that encapsulates one or more smaller GVs. During the incubation, the membrane of flaccid vesicle invaginated and closed to form the inner vesicle of an OVV engulfing a part of the bulk aqueous phase. Using the GV-to-OVV transformation, an OVV that has different aqueous contents in each membranous microcompartment was constructed.