The characterization and understanding of the structure of polymer nanoparticles and bulk-like phase behavior of amphiphilic triblock copolymers of poly(acrylic acid)-b-poly(methyl acrylate)-b-polystyrene in water/tetrahydrofuran (THF) solvent mixtures is strongly dependent on block composition as well as solvent composition. The block copolymers were dissolved in THF in the presence of an organic counterion. Upon the slow addition of water, a variety of structures were observed including phase-separated nanoparticles, bulk-like lamellar phase separation, spherical, cylindrical, and disk-like micelles, as well as toroidal assemblies. The specific structure formed was dependent on the architecture of the triblock copolymer, the amount of counterion present, and the water to THF volume ratio. This work focuses on the structure of polymer nanoparticles and networks formed in low water content systems. The size of the nanoparticles and whether separated nanoparticles vs. an interconnected network was formed can be controlled via solvent composition. Importantly, both the nanoparticles and network phases contain their own inherent nanostructure due to local phase separation of the block copolymers. Cryo-transmission electron microscopy, traditional transmission electron microscopy, and neutron scattering were used to examine these samples.