Puberty is a time of physical, social, and cognitive changes with direct implications for adolescents' development and long-term well-being. Although scientific knowledge of puberty is growing, there remains little information about how puberty impacts the social and cultural experiences of Latino boys in the U.S. The goal of this project is to understand how biological and physical markers of puberty relate to everyday experiences of boys from Mexican-American families. This is a large and rapidly growing group in the U.S. who are at increased risk for high school drop-out, substance use, and delinquency. The study will include interviews with 400 Mexican-American families who have a male adolescent between the ages of 12-16 years old. The project will investigate how boys' pubertal development influences social interactions with their parents, teachers, and friends, and examine how these biological and social factors together impact their mental health and well-being. The research will provide critical information to families, community members, and health care providers about the ways in which puberty shapes the context and development of Latino boys. Adolescents and their parents will complete in-person interviews that assess puberty, daily stressors, parent-child relationship factors, and key developmental outcomes: mental health, risky behaviors, academic functioning, and ethnic identity. Adolescents will also provide saliva samples to capture biological markers of development measured by levels of puberty hormones. Adolescents will be followed up one year later to assess long-term changes in these same outcomes. The goals of the project are to study the connection between pubertal development and Mexican-American boys' experiences in school and community contexts; test the association between puberty and parent-child relationship factors; and examine how the link between puberty and youths' mental health, risky behaviors, academic achievement, and ethnic identity is explained by both positive and negative social experiences. The Latino population of the U.S. is growing, and ethnic-racial disparities in social and economic well-being continue. Understanding biological, social, and cultural determinants of Mexican-American boys' development will contribute to basic knowledge that informs approaches to addressing this critical societal challenge. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.