Lev Vygotsky proposed that psychology should go beyond immediate experiences; psychology is about processes hidden from direct observation. In Vygotskian cultural-historical psychology scientific activity is understood as study of the world that is based simultaneously on method and methodology. The aim of cultural-historical psychology is to describe directly non-observable psychological structures that underlie manifest behavior. This chapter contains several examples to prove that there is no one-to-one correspondence between the sensory world and reality and even less so between sensory-based and semiotic representations. It discusses one example that follows from application of methodological principles of the cultural-historical approach at the relatively local level of theory-building. Cultural-historical psychology is structural-systemic. Finally, the chapter discusses the two issues at a more local level, that of internalization and that of lexical assumption. Structural-systemic cultural-historical methodology rejects the unidirectional '(cultural) environment-determines-mind' account of the development of mind.