The course presents the basic mechanisms that lead to the formation of micro or nanostructures in polymer blends and in bulk or aqueous copolymer systems. • The first part is devoted to the elementary mechanisms driving the formation of micro and nanostructures in heterogeneous polymer systems. More precisely, thermally or chemically driven phase separation in polymer mixtures (spinodal decompositions) or the mechanisms controlling the more elaborated structures spontaneously formed in copolymer systems are investigated. • A second part will allow to travel in the scale of structuring: from immiscible polymer blends, compatibilized or not, to nanometric and organized heterogeneous systems that can only be obtained by increasing the fraction of block copolymer within the material. Throughout the course, examples will be developed progressively from "micro" to "nano"; examples of commercial materials or from advanced research. • The third part concerns self assembly of amphiphilic copolymers (polymersomes and micelles) : the effect of the composition and the chemical microstructure and the experimental conditions, such as pH, temperature, ionic strength, concentration…) on the size and morphology of the resulting nanoobjects will be studied.