Environmental exposures, breast development and cancer risk: Through the looking glass of breast cancer prevention

•Timing matters during the life course to identify when an exposure influences breast development or cancer risk.•Transdisciplinary research can accelerate knowledge about environmental exposures and mechanisms related to breast development and cancer risk.•Animal–human research discovery of windows of susceptibility, and pathways enhances to derangement of normal breast development and cancer risk.•The Interagency Breast Cancer and Environmental Research Coordinating Committee was tasked to review the science, identify gaps, and evaluate options for dissemination of result. This review summarizes the report entitled: Breast Cancer and the Environment: Prioritizing Prevention, highlights research gaps and the importance of focusing on early life exposures for breast development and breast cancer risk.