Adolescence is a time of development in the brain and microbiome, including the microbiome present in the mouth called the oral microbiome. Alcohol use often begins and escalates during adolescence, which can cause changes to the oral microbiome leading to changes in the brain. The alcohol specific changes to the oral microbiome and the brain may make adolescents more vulnerable to a lifelong struggle with alcohol use disorder. This study will collect (1) saliva to assess the composition of the oral microbiome and (2) brain measurements using magnetic resonance imaging (MRI) across adolescents who may or may not use alcohol. Findings from this study will help form a more thorough understanding of the biological consequences of adolescent alcohol use, with the long-term goal of informing novel prevention and intervention efforts.