Polymerization-induced self-assembly (PISA) is a powerful method for the synthesis of polymeric kinetically frozen core nanoparticles. However, the PISA synthesis of biologically important polymeric fluidic materials is unexplored. Herein we present a liquid-liquid phase separation mode PISA. The proof of concept is established by means of complex coacervation in visible light-initiated RAFT dispersion polymerization of anionic monomer in the presence of a protonated polyethylenimine in water at 25 °C. We demonstrate a stage-by-stage nano to micron droplet growth mechanism via an increase in growing chain DP or electrical neutralization. Liquid coacervate droplets and their glassy nanowires or vesicles can be interconverted upon changing the ethanol/water solvent. As such, tunable construction of coacervate droplets and nanowires or vesicles can be achieved using this smart PISA method.