Increasing availability of tablets at home—even for the youngest ones— is a fact. Therefore, research on mathematical play and learning apps is of growing importance. The project MaiKe (Mathematik im Kindergarten entdecken) develops its own and mathematically sound app. MaiKe regards and refl ects in concept, development and design both developmental psychology and mathematics educational findings and research. MaiKe takes into account the broad range of competencies which are considered to promote a successful school beginning. The concept and design information about the app as well as concrete examples of technical realisation and use are given.