A method of generating an internally fixed lipid vesicle, comprising: providing a precursor lipid vesicle that contains an aqueous interior enclosed by a lipid membrane, wherein the lipid membrane of the precursor lipid vesicle is non-permeable to a crosslinker; permeabilizing the lipid membrane transiently to generate a permeable vesicle; contacting the permeable vesicle with an inactive activatable crosslinker, whereby the inactive activatable crosslinker enters the permeable vesicle; allowing the permeable vesicle to return to a non-permeable vesicle; removing any extravesicular crosslinker; and activating the inactive activatable crosslinker to allow crosslinking to occur inside the non-permeable vesicle, whereby an internally fixed lipid vesicle is generated.