The colloidal nanoparticles produced from bulk metal by laser ablation in water usually oxidize during aging. Such transformation could be used as a tool for nanoarchitecture if the control parameters are known. Here we studied in detail the transformation of copper-based nanoparticles in water during the colloid aging and the evolution of nanoparticle morphology at various temperatures. The spherical Cu@Cu2O core-shell nanoparticles were produced by laser ablation of Cu target in water. The aging of prepared colloid was investigated in situ by UV–visible absorption spectroscopy. The nanoparticle morphology and composition were characterized by scanning and transmitting electron microscopies, X-ray photoelectron and Raman spectroscopies. The aging of colloidal nanoparticles resulted in morphology changes and composition transformation to CuO. The nanoparticle sizes enlarged due to Ostwald ripening and aggregative growth either isotropically at room temperature (25 ℃) or by forming elongated nano-spindles at temperature above 35 ℃. The occurred transformation was characterized by Kolmogorov-Johnson-Mehl-Avrami approach which allowed to extract the activation energy of the process. The obtained results are useful for both nanoarchitecture and gaining colloid stability.