Kimura and co-workers prepare vesicles with a homogeneous size distribution using both membrane fusion and membrane fission of various combinations of three amphiphilic polypeptide assemblies. Controlled self-assembly leads to nanotubes and nanosheets, with the nanosheets fusing to the end of the nanotubes. Subsequent fission gives a closed 60 nm vesicle leaving behind a shortened nanotube. The size of the vesicles is related to the diameter of the nanotube, therefore by using nanotubes as a structural template it is possible to regulate the size of vesicles upon the membrane fission process. (doi: 10.1002/bip.22903)