Online communities offer great potential for sourcing future innovations. While organizations search for inspiration and innovations outside their organizational boundaries to stay competitive, individuals innovate to solve their own needs and subsequently freely reveal these innovations. Online communities constitute a virtual space for individuals to share ideas, socially interact, collaborate, and build on others’ ideas. In this dissertation, I investigate how these social interactions influence the generation of ideas and the ongoing idea development in online communities. The three studies of this dissertation use two unique large datasets that allowed the investigation of social interactions and their contents. In doing so, topic modeling and social network analysis techniques build the methodical foundation to measure latent content representations of the information that is exchanged in online communities. Regarding the generation of new ideas, this dissertation includes two empirical studies that focus on the content that individuals access through their social peers. The first study reveals that the combination of redundant and non-redundant information favors idea newness. In particular, brokers accessing diverse social information benefit from redundant content for generating new ideas. In contrast, non-redundant contents have detrimental effects on brokers’ social non- redundancy regarding brokers’ idea newness. The second study takes a time-dependent view on social interactions and finds that a temporal separation between inspiration and focus on specific contents leads to more innovative outcomes of individuals engaging and innovating in online communities. By focusing on the ongoing collaborative idea development process in online communities, the third study investigates how social influences shape the trajectory ideas take after they got initially shared. The findings of the third study show that social impact theory helps explain how social influences affect the development directions of ideas in online communities. By taking different perspectives on innovative endeavors in online communities, this dissertation contributes to the literature on online communities, social networks, and user innovation. Specifically, this dissertation emphasizes the importance of social interactions for innovations and this relationships’ dependence on the actual content, timing, and social impact of social interactions.