Traditional structural studies have focused on single-Fab footprints to explain antibody potency, breadth, and mechanisms of neutralization. Yet in vivo, antibodies act as full, IgG molecules—bivalent by design, gaining not only epitope-mapping capacity from each Fab arm but also greater avidity and enhanced neutralization through multivalent binding. Understanding this multivalency is essential to uncovering how antibodies truly operate at the viral surface. We combine molecular-dynamics simulations, functional neutralization and binding assays, and cryo-EM to reveal how IgG multivalency—via antigen clustering and higher-order binding geometry—empowers even low-affinity antibodies to achieve potent neutralization and drives variant-specific differences in antibody efficacy. To further dissect this spatial dimension, we are developing DNA-based nanostructure “scaffolds” that precisely control antigen spacing at the nanoscale, offering a unique platform to probe how antigen organization governs antibody engagement and viral neutralization.