We highlight that polymer systems provide extremely good model systems for basic researches on soft-matter physical science. Their inherently large characteristic space-time scale enables us to elucidate the space-time organization of self-assembling processes via phase transitions in such a level that cannot be easily attained by small-molecule systems having small space-time scales. We emphasize also the fact that SANS studies are crucial in elucidating a whole spectrum of hierarchical structures of soft-matters and their responses to external stimuli. As an example, we reviewed some experimental results on space-time organization of phase-separating structures during spinodal decomposition of dynamically symmetric molecular mixtures and discussed universality in this context between polymers and small molecules.
