Mixtures of long- and short-chain phospholipids can spontaneously form uniform unilamellar vesicles (ULVs) with diameters 50 nm (polydispersities of <0.3) or less. The morphology of these ULVs has mainly been characterized using small angle neutron scattering (SANS), a technique highly suited for the study of hydrogenous materials. Once formed, these ULVs have turned out to be highly stable and show great promise as imaging and therapeutic carriers.