Polymerization-induced self-assembly (PISA) is a versatile method that enables the synthesis of diblock copolymer nanoparticles in many solvents. In particular, sterically-stabilized spherical nanoparticles in non-polar solvents represent an interesting model system. We recently prepared a series of such spheres with mean diameters that strongly depended on the degree of polymerization of the stabilizer block. Recently, spin-echo small-angle neutron scattering (SESANS) has been shown to enable precise characterization of the microstructure of polymer colloids. We plan to use this technique to study the structure of poly(stearyl methacrylate)-poly(benzyl methacrylate) (PSMA-PBzMA) spherical nanoparticles to assess the morphology of the stabilizer and core-forming blocks and the degree of solvation, connecting the localized polymer structure to the final nanoparticle size.