This special issue is devoted to Vasily Davydov and the ground-breaking work that he introduced together with Daniil Elkonin. Their work, substantiated by many years of rigorous experiments, presents a theoretical extension and an educational concretisation of foremost Lev Semyonovich Vygotsky’s cultural historical theory and Alexei Leontiev’s activity theory. In the West, the curriculum in mathematics for the youngest students stemming from Davydov’s longitudinal series of experimentsis most known as the Davydov curriculumor program. Jean Schmittau together with her colleague Ann Morris is perhaps among the first to “import” the Davydov program into the US (Schmittau & Morris, 2004). There are other established implementations of the Davydov curriculume specially in the US, such as the project “Measure up” in Hawaii led by Barbara Dougherty (Dougherty & Slovin, 2004). More recently, Martin Simon (Simon & Placa, 2012) has been leading a five-year research project inquiry into the mechanisms of mathematics conceptual learning, where the Davydov curriculum is used as the main framework to shift the curriculum in mathematics education in the US. To date, the program has become known in other countries as well and a growing number of researchers are exploring its tenets and potential implications in mathematics education. Interestingly, the Davydov program is more frequently referred to within the research field of early algebraisation (see for e.g.,Cai & Knuth, 2011) and researchers are looking to Davydov’s heritage as a source of inspiration for new developments and new perspectives on what and how to teach elementary mathematics, thus introducing a new paradigm of psychological, mathematical, and pedagogical knowledge in the field of mathematics education.