Coacervation is an electrostatically-driven liquid-liquid phase separation process, resulting from the association of oppositely charged macro-ions. In this framework, core-shell-corona (CSC) micellar complexes result from the coacervation of the charged shell of a polymer micelle and an oppositively charged block-copolymer. Here, we propose a time-resolved uSAXS study of the dynamic hierarchical self-assembly of CSC micellar complexes in water formed by the coacervation between positively charged PLL chains and negatively charged PAA brushes of core-shell PSS-PAA micelles, presenting PEG brush on the complex exterior. We aim to study 1) the micellization process (PS-PAA self-assembly); 2) the coacervation process (adsorption of PL-PEG polymers on PAA corona brush); 3) the coacervation reversibility (desorption of PL-PEG polymers) by varying the polyelectrolyte charge density.