The present invention relates to a stimuli-responsive composition that comprises a polymer, a solvent and a substance having a predetermined function. One embodiment of the present invention is a composition comprising a block polymer, a solvent and a substance having a predetermined function. The present invention also relates to an ink composition containing the composition, an image-forming method and an image-forming apparatus using the composition, and a recording medium applying the composition. Further, the present invention relates to an ABC type block polymer compound wherein the polymer is an ABC type triblock polymer, and wherein at least one of the blocks in the triblock polymer changes in nature from solvophilic to solvophobic or from solvophobic to solvophilic in response to stimuli, and more preferably, the A component, then the B component, and finally the C component respond to the stimuli.