<p>From both ecological and economic viewpoints, emulsion polymerization-induced self-assembly (PISA) using water as a solvent is an attractive strategy for producing polymeric nanomaterials for diverse applications. However, traditional emulsion PISA (TE-PISA) usually faces challenges like the generation of large agglomerates, limited morphology evolution, and poor reproducibility. In this work, we demonstrate that asynchronous chain extension of macro-CTAs leads to poor controllability of emulsion polymerization, which is the root cause of the above problems. Furthermore, an elaborately designed seeded emulsion PISA (SE-PISA) strategy ensures superior controllability of the emulsion polymerization (synchronous chain extension of macro-CTAs and controlled morphology evolution), which is demonstrated to be a robust methodology for overcoming these challenges. The universality of this methodology was verified by varying hydrophobic monomers and macro-CTAs across different SE-PISA formulations. Synthesis of micellar seeds and the subsequent SE-PISA can be both conducted in water, which is obviously more economical and environmentally friendly. Moreover, the fabrication of waterborne nanomaterials by the SE-PISA strategy shows superior reproducibility. This work provides a green, environmentally friendly, efficient, and universal strategy for producing high-quality polymeric nanomaterials.</p>