European cities face complex economic, social and environmental challenges. To address these challenges, cities seek new approaches. A currently popular approach is urban labs (living labs and city labs), in which local governments engage in solving problems together with other stakeholders in urban development. However, clear guidelines are needed concerning types of problems for which urban labs are most suited and how urban labs can best be organised and integrated into formal local government organisations. The URB@Exp project aims to develop such guidelines by reviewing experiences of urban labs, and conducting action research in urban labs in five European cities.