Lipid-based assemblies, like liposomes, lipid nanoparticles (LNPs), and emulsions, are widely used to encapsulate and protect therapeutic molecules. Several lipid-based drug delivery platforms are used clinically as vaccines and to treat diseases ranging from fungal infections to cancer. However, each formulation must be carefully optimized. Encapsulation and retention of drug molecules depends on the lipid composition, buffer components, and processing conditions while the uptake and delivery performance depend on the size, surface functionality, and charge of the carriers. This project will use complementary characterization methods including small angle X-ray and neutron scattering (SAXS and SANS) and cryogenic electron microscopy (CryoEM) to understand the detailed structure of drug delivery systems as well as their stability throughout common processing conditions such as shear, exposure to air, dilution or concentration, freezing, lyophilization, and long-term storage. Linking structure with stability and activity of lipid-based delivery systems will aid in the design of new formulations with improved properties.