Fe-Cu binary alloy is an appropriate prototype for reactor pressure vessel steels (RPV), since segregation of Cu is one the main reasons for embrittlement in RPV steels under irradiation. Interestingly, long-term thermal aging also can emulate this radiation-induced segregation. For a comparative study, a series of Fe-Cu alloys (0.1–1.4 at.% Cu) were subjected to: (i) Aging at 773 K for: 1, 3, 5, 8, 25, 50 and 100 h; and (ii) Irradiation up to 1 dpa with 8 MeV proton beam. Segregation starts as fine Cu-rich coherent spheres that evolves into cylinders beyond a threshold size and small-angle neutron scattering (SANS) is especially suited to study this phenomenon along with its complex transition. The current study will explore the temporal evolution of segregation by combining ex-situ SANS with complementary techniques 3DAP & TEM, followed by in-situ SANS at 773 K. Combination of these complementary techniques would provide comparative perspectives and valuable insight into evolution of solute segregation process.