Romantic relationship formation and the engagement in sexual behaviors are normative and salient developmental tasks for adolescents and young adults. These developmental tasks are increasingly viewed from an ecological perspective, thus as strongly embedded in different social contexts. This volume brings together seven recent empirical studies that investigated different aspects of adolescents’ and young adults’ romantic relationships and sexuality, and the linkages with various characteristics of relations with parents, peers, and partners. These studies were conducted in six Western countries, including Australia, Belgium, Canada, Germany, the Netherlands, and the USA. Three studies examined the formation of young people’s romantic relationships, and the other four studies focused on youth’s developing sexuality. Together, they employed a diverse range of state-of-the-art research methods, including online questionnaires, computer-assisted interviews, daily diary assessments, and observations of dyadic interactions. In the editorial chapter, these recent advances in empirical research are discussed and framed within two important changes in the theoretical perspectives on young people’s emerging romantic relationships and sexual activity: from risky behaviors to normative tasks, and from individual to contextualized processes. Throughout this volume, important directions for future research are suggested, specifically focusing on how to better incorporate the interrelational perspective into empirical research on these topics, and how to further bridge the gap between the research fields on romantic relationships and sexuality.