RADAR (Research on Adolescent Development And Relationships) is a longitudinal study that started in 2005. RADAR focuses on the interactions and conflicts of adolescents with parents and peers, their emotional state, personality, identity, and internalizing and externalizing problem behavior. RADAR investigates the development of 800 participants from early adolescence to adulthood. Additionally, their parent(s), intimate partner, brother or sister, and (best) friend also participate in the study.