In the current economic landscape, users have been shown to be a highly promising and fertile external source of novel innovations. First, this chapter focuses on the importance and magnitude of the open innovation paradigm and collaborative practices. Second, this chapter underlines, through a body of work and on a wide variety of industries, the phenomenon of user innovation and stresses a theoretical and empirical development of the concept. Third, this chapter paints a striking picture of the trend of co-creation with users and shows that co-creation with users has grown in recent years with the deployment of online communities, interactive platforms for creation, self-service toolkits and companies specialized in crowdsourcing. Finally, this chapter provides details on two favored and atypical co-creation targets with a high potential for innovation – lead users and emergent nature consumers – and discusses the benefits and limits of co-creation and co-innovation practices with users.