The present invention relates to a method for preparing a protocell in form of a giant unilamellar vesicle, which comprises the following steps: a) providing a water-based droplet encapsulated by an outer polymer shell, which borders the inner space of the droplet, wherein the droplet has a maximum dimension of 0.5 μm to 1,000 μm, wherein the inner space of the droplet contains at least one lipid, b) transforming the lipid content of the droplet into a lipid bilayer which is arranged at and covers the inner surface of the polymer shell and oil phase in order to form a polymer shell-stabilized giant unilamellar vesicle, c) optionally incorporating one or more proteins and/or nuclei into the polymer shell-stabilized giant unilamellar vesicle provided in step b) and d) optionally removing the polymer shell and oil phase from the polymer shell-stabilized giant unilamellar vesicle and optionally transferring it from the oil to the water phase.