This article is devoted to the analysis of the reasons for the occurrence of diffraction fringes in the cores of the core-shell nanoparticles Cu/SiO2. Moire and diffraction fringes are observed while studying the nanoparticle cores under a transmission electron microscope. The formation of diffraction fringes is closely connected to the mechanism of nanoparticle formation under study and appears to be its consequence, letting us develop a hypothesis of metastable phase formation in nanoparticle cores. In our opinion, the emergence of diffraction fringes in cores of copper is connected to clasterisation in solid solution oversaturated with silicon alpha-Cu with the diffused interphase state. (C) 2016 Published by Elsevier B.V.