The article by E. P. Favvas and A. Ch. Mitropoulos discusses the concept of spinodal decomposition in phase separation. Spinodal decomposition occurs when a system crosses the spinodal locus in a phase diagram, leading to spontaneous phase separation without the need for nucleation. The spinodal is defined by the unstable region in the phase diagram, where the second derivative of the free energy of mixing is negative. The Cahn-Hilliard equation describes the kinetics of this process. The authors also present a schematic comparison between nucleation and spinodal decomposition, highlighting that nucleation is characterized by large fluctuations in degree but small in extent, while spinodal decomposition is characterized by small fluctuations in degree but large in extent. This results in a high interconnectivity of the two phases. The article includes figures illustrating the nucleation and growth process, as well as the spinodal decomposition mechanism, and discusses the conditions under which each process occurs.The article by E. P. Favvas and A. Ch. Mitropoulos discusses the concept of spinodal decomposition in phase separation. Spinodal decomposition occurs when a system crosses the spinodal locus in a phase diagram, leading to spontaneous phase separation without the need for nucleation. The spinodal is defined by the unstable region in the phase diagram, where the second derivative of the free energy of mixing is negative. The Cahn-Hilliard equation describes the kinetics of this process. The authors also present a schematic comparison between nucleation and spinodal decomposition, highlighting that nucleation is characterized by large fluctuations in degree but small in extent, while spinodal decomposition is characterized by small fluctuations in degree but large in extent. This results in a high interconnectivity of the two phases. The article includes figures illustrating the nucleation and growth process, as well as the spinodal decomposition mechanism, and discusses the conditions under which each process occurs.