The article is devoted to the problem of development of thinking at the level of images in ontogenesis; it is emphasized that the empirical picture of the world is based on a system of categories, on sensuous-practical experience, on rational procession of the latter in relation to different executed activities, and on acquired scientific data. The contents of mental images are basically constituted of complex dynamic psychological formations differing in the level of their generality, stability, and schematicity, and by their origin. Thinking in images is characterized by significant age and individual differences which are manifested in particularities of image formation, in particular ways they are manipulated and transformed (both mentally and in presence of visual supports), in corresponding perceptual activity, and in emotional-subjective attitude to the environment. Particular attention is given to the mechanism of mental representation as a specific activity which possesses its own contents, highly complicated structure, and requires specific conditions for proper development.