The aim of this article is to analyse the transition period in the history of illustrating children’s educational books on the material of Russian-language publications. It is the period in which the function of an intermedial representation gradually develops from emblematic to encyclopedic and narrative-figurative images. This process is related to the literary history of children’s books and their genre transformations. In the last third of the 18th century, children’s literature in Russia was formed as an independent direction with its special goals, and the basis for further search for specific methods of children’s book design, including educational ones, was laid. In the first quarter of the 19th century, the children’s book had a typical European visual design and continued the trends inherited from the 18th century: translations, borrowings, and revised texts in publications often copied illustrations rather than made new ones. A new stage came at the end of the 1820s, when Russia was actively developing independent children’s literature, and professional authors and criticism appeared. It was the time of the pedagogical experiments of Vasily Zhukovsky. This article does not claim to analyse Zhukovsky’s pedagogical activity comprehensively, but this activity is significant for the subject-matter of the study. In his pedagogy, Zhukovsky went to a new level when searching for intermedial ways of transmission of the universal coherence of phenomena, the systemic representation of knowledge about the world, and the ideas of the world as a system. The search, though much slower, was also observed in contemporary children’s books. The integration of cognitive and didactic functions in the Russian-language children’s book of the 18th century resulted in a mix of different principles of illustration in one publication. These principles are: (1) emblematic: the title, image, and text form a three-part structure; (2) encyclopedic: the sheet contains separate numbered images of the same type of objects excluded from the visual context; (3) narrative: the plot, expressive and figurative, including caricature, illustrations are readily used in an educational book due to their persuasiveness. Each of these principles has its own ways of displaying coherence. An encyclopedic illustration shows an object in a series of similar ones, in an enumeration, shows the structure of the object. An emblem gives its symbolic and allegorical interpretation. A narrative illustration shows its functions and its involvement in causal relations, depicting the environment of events and objects. The children’s book of the studied period tends to integrate all these ways. While the emblem as an independent intermedial genre degrades, certain elements of the emblematic tradition are actively borrowed by new forms of publications. The emblem gives the European book of modern times the most important intermedial tools for displaying universal coherence, the world as a system. The change of the epochs leads to an inevitable blurring of the meaning of the emblematic sign. The transitive nature of the analysed period is expressed in the search for a new intermedial form of coherence, similar to the lost emblematic bimediality of the text and illustration in terms of effectiveness. In the search for such a form, encyclopedic publications that claimed to be all-encompassing use the emblematic and narrative principles of illustration. In turn, the narrative illustration, driven by a similar desire for inclusiveness, consistency, and universality, absorbs the emblematic and encyclopedic principles.