In this chapter we present an online social network created for the study of life transitions of young adults. We first give a brief overview of the overall goals of the study and outline two research questions to be studied with the online social network. We then present the rationale for using and developing our own network. Next, we describe the online social network: the concrete steps of creating the network, its functions and characteristics, and first results based on a sample of 365 young adults. These first findings reveal that the social network has so far not worked as intended: Participants are reluctant to use the network and more effort is required in motivating them to actively use it. We discuss possible reasons for the serious difficulties in attracting participants to engage with the network and relate the problems faced during the development and maintenance of the network. Finally, we outline alternative possibilities of using online social networks in future research.