Lateral phase separation and budding of giant vesicles prepared by electroformation with a model mixture, 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC)/1,2-dipalmitoyl-sn-glycero-3-phospho- choline (DPPC)/Cholesterol (Chol), were observed directly by fluorescence microscopy. It was found that the separation after a short retardation time was a fast process and the domains thus formed were regularly distributed on the surface of the vesicles. Budding of the microdomains occurred one by one and the time to finish a budding process was less than 0.5 s. The coupling of the separation and budding stopped further fusing and growing of the microdomains.

Key words: giant vesicle, lateral phase separation, budding