Thermodynamic/dynamic modeling of liquid immiscibility in silicates is seriously hindered due to lack of in situ investigation on the structural evolution of the melt.In this work,atomic-scale structural evolution of a classic binary silicate immiscible system,SiO2-TiO2,is tracked by in situ high energy X-ray diffraction(HE-XRD).It is found that both the configuration of[SiO]and the polymerization between them are closely coupled with embedment and extraction of the metallic cations (Ti4+).[SiO]monomer goes through deficit-oxygen and excess-polymerization before liquid-liquid separation and enables self-healing after liquid-liquid separation,which challenges the traditional cognition that[SiO4]monomer is immutable.Ti4+ cations with tetrahedral oxygen-coordination first participate in the network construction before liquid separation.The four-fold Ti-O bond is broken during liquid separation,which may facilitate the movement of Ti4+ across the Si-O network to form TiO2-rich nodules.The structural features of nodules were also investigated and they were found highly analogous to that of molten TiO2,which implies a parallel crystallization behavior in the two circumstances.Our results shed light on the structural evolution scenario in liquid immiscibility at atomic scale,which will contribute to constructing a complete thermodynamic/dynamic framework describing the silicate liquid immiscibility systems beyond current models.