Recent advances in molecular biology, genomics, and epigenomics has now provided paradigms for understanding long term effects of stress. This presentation will focus on intergenerational transmission of trauma as a particularly enduring effect of stress. Most of the research has been conducted on adult children of Holocaust survivors, but has now generalized to include children of other trauma survivors such as children born to pregnant women who survived the world trade center attack on 9/11. The research has evolved into one that explains the contribution of early environmental experiences-including parenting-on highly conserved molecular and genomic processes. These changes in and of themselves do not signify pathology, but provide a paradigm for understanding long term effects of profoundly important events. The work has already led to a better understanding of biological risk factors for PTSD and predictors of outcome in response to trauma.