Certain early life exposures such as malnutrition and abuse are known to affect health outcomes later in life. However, these relationships are highly variable, dependent on many factors including the unique genetics and environments of each individual. Furthermore, recollections of life history can be extremely inaccurate. Consequently, it can be difficult to identify high-risk individuals, to recommend effective treatments or to assess treatment effectiveness in a timely manner. Recent studies have shown that many exposures are encoded in the methylation levels of blood DNA including cigaratte smoke, age, trauma, diet, stress and socio-economic position. My goal is to characterize the associations between blood DNA methylation levels and a wide variety of exposures throughout life, particularly early exposures and those later exposures that appear to mitigate the health outcomes of early exposures.  These characterizations may then suggest more targetted experiments to develop DNA methylation-based assays to help piece together exposure histories in order to identify high-risk individuals, to select interventions likely to improve health, and to monitor the effectiveness of ongoing interventions.