This special issue is devoted to the topic of tangible user interfaces and children. It emphasizes research on tangibility that transcends system descriptions, focusing on the empirical support of theories and design guidance. The papers result from the organization of a workshop at the CHI 2009 ACM conference in Boston, USA. As an introduction to this issue, empirical evidence is discussed for the potential benefits that using TUIs may have for children. Next, we focus on the impact of tangibility in terms of usability, learning, collaboration, and fun. Finally, we suggest directions for future work and outline the papers that are included in this special issue.