The project is aimed at first-principles understanding of early stages of polymer foam evolution including nucleation or phase separation by spinodal decomposition and coalescence of cells. Experimental methods including novel laser-induced foaming as well as established techniques (pressure or temperature induced foaming, spinodal-route to foaming) will be combined with analysis of foam morphology, thermodynamics, diffusion and relaxation phenomena. Based on the improved understanding of nucleation and coalescence the methods of nano-/micro-cellular foam preparation will be assessed and optimized. Systematic experimental studies of nucleation, spinodal decomposition, Ostwald ripening and coalescence phenomena will be accompanied by the development of thermodynamically consistent mathematical models combining Cahn-Hilliard and self-consistent field theory approaches with advanced equations of state and description of relaxation processes. Coalescence and drainage in late stages of foaming will be modeled by the hybrid discrete element method including interfacial and osmotic effects.