In this session, on work in progress in the NHLBI sponsored severe asthma research program, there are four presentations planned to provide the learner with a cutting edge, data driven understanding of the clinical features of pediatric and adult severe asthma. Each presentation will cover the context, rationale and recent progress in addressing clinically relevant questions in severe asthma pathobiology, diagnosis and management, including baseline cross-sectional data on recruited healthy and asthmatic subjects, risk factors for asthma exacerbations, and, importantly, the change in pathophysiologic features of disease and phenotypes over time and their association with clinical outcome.