This chapter identifies the main conceptual aspects of dynamic assessment (DA) and elaborates the relationships between various DA approaches and the Lev Vygotskian theoretical tradition. Vygotsky connected the task of studying the emergent psychological functions with two additional phenomena, "sensitive periods" and imitation. The chapter introduces the early attempts to challenge the predominantly static approach to assessment associated with the intelligence-testing tradition. It discusses the role of Vygotsky's notion of the Zone of Proximal Development (ZPD) in shaping DA approaches together with an elaboration of the different paths taken in Russia and the West by the DA concept. The "technique" of ZPD assessment sketched by Vygotsky included modeling, starting the task, providing hints, etc. The developmental aspect of ZPD is related to DA of cognitive modifiability that focused on the qualitative changes in the child's cognition and the emergence of the new forms of reasoning and problem solving.