Diagrams drawn from cryo-electron micrographs of cross-sections through vitrified films of various types of liposomes and DNA-liposome complexes. SUVs are small unilamellar vesicles that condense nucleic acids on the surface and produce “spaghetti and meatballs” structures. MLVs are multilamellar vesicles that appear as “Swiss rolls” after mixing with DNA. BIVs are bilamellar-invaginated vesicles produced using a formulation developed in our laboratory [1]. Nucleic acids are efficiently encapsulated between two bilamellar-invaginated structures (BIVs).