This chapter presents the ideas and notions that formed cultural-historical psychology. It first introduces Humboldt's theory of language, itself embedded in the philosophy of language of German Romanticism. Describing the nature of language, According to Humboldt, a concept is generated by tearing it off from the "moving mass of ideas". A first "migration" of the Humboldtian inner form is seen in his pupil Heymann Steinthal, whose psychologization of Humboldt's philosophy of language and of the inner form was important for its survival, foremost in Eastern Europe. After this brief look at Steinthal, the chapter discusses the adoption of Humboldt-Steinthal by Potebnia, transferring also the notion of inner form to the East. The last part of the chapter is devoted to Vygotsky, a critical reader of Potebnia, who nevertheless stayed within the tradition opened by Humboldt's language philosophy.