In 2008, the research center "Individual Development and Adaptive Education" was constituted by the Goethe University, the German Institute for International Educational Research, and the Sigmund Freud Institute, all located in Frankfurt am Main, Germany (http://www.idea-frankfurt.eu). The research of the center focuses on the development of children in preschool, kindergarten, and primary school age by including and combining cognitive, neuro-cognitive and socio-emotional factors. The Special Issue "Early Years" reports about the research activities concerning mathematics learning in the early years.