Aiso Heinze, Prof. Dr. rer. nat., is Head of the Department of Mathematics Education at the Leibniz Institute for Science Education (IPN) in Kiel (Germany) and Full Professor for Mathematics Education at Christian-Albrechts-Universität zu Kiel. He studied mathematics and chemistry at Carl von Ossietzky-Universität Oldenburg and received his Ph.D. in mathematics in 2001. In 2004, he received the postdoctoral lecture qualification (Habilitation) for mathematics education from the Universität Augsburg. After two years as Privatdozent at the Ludwig-Maximilians-Universität München and one year as professor for mathematics education at the Universität Regensburg he was appointed as head of the newly established Department of Mathematics Education at the IPN in Kiel. Aiso Heinze's research interests are related to the development of mathematical competence at primary- and secondary-school level. He is involved in a longitudinal study on competence development of primary-school children with migration and nonmigration background and in a study on the development of high-school students’ competence in reasoning and proof. In NEPS he is a member of the mathematics group at the IPN to investigate the development of mathematical competence over the life span.