Being bullied is a major stressor for many adolescents and it is recognized as a public health concern worldwide. Adolescents who are exposed to bullying are at increased risk for mental and physical health problems, which could even perpetuate into adulthood. Unfortunately, current understandings of how bullying can pose such deleterious effects remain poor, thus limiting our ability to inform prevention and intervention efforts. This project addresses this fundamental gap and substantially extends prior research in two unique ways. First, I will examine fine-grained processes as they occur within adolescents in real-time in their real-life as a crucial pathway for uncovering mechanisms underlying the negative effects of bullying. Second, I will adopt a multilevel perspective to examine the dynamic interplay between multiple psychological and biological processes and how they unfold over time. In this regard, I will examine the possibility that bullying influences gene expression processes resulting in a gene expression profile that increases risk for health problems. In a first study, I will use a longitudinal measurement burst design, allowing me to examine how bullying exposure can influence within-person processes over time at the daily level. I will assess psychological (e.g., emotional) and physiological (e.g., HPA-axis) functioning in situ, and I will use transcriptional profiling to examine how gene expression changes over adolescence as a function of bullying. In a second study, I will utilize data from the Netherlands Twin Register to identify monozygotic twins who differ from each other in their history of victimization in adolescence and examine their gene expression profiles in early adulthood, while accounting for genetic confounds. Together, this research will offer unprecedented insights about short- and long-term interplays between psychological, physiological and molecular processes through which bullying may get into the mind and under the skin.