My research, teaching and clinical contributions all focus on the pathophysiology of hematological diseases. In the laboratory we largely investigate the molecular mechanisms of iron transport and delivery to erythroid cells for the purpose of heme biosynthesis. Our primary experimental approach is to characterize the molecular genetic basis of inherited “iron deficiency” anemias in the mouse by using positional cloning. I, my colleagues and collaborators have made several seminal contributions to the field or iron metabolism including identification of the iron transporter and reductase essential for iron acquisition from the transferrin cycle. Most recently, we have identified a gene responsible for a congenital predisposition to iron deficiency in humans, opening up the possibility that iron deficiency, largely conceived of as an environmental disease, may well have a significant genetic component. My clinical and teaching contributions are an equal part of my academic career. I am the primary hematological pathologist at Children’s Hospital Boston. As such, I am responsible for the pathological evaluation of hematological diseases, including congenital bone marrow diseases, leukemias, and lymphomas. Here, and through my involvement in the Harvard Medical School year two hematology course I have had a substantial commitment to the education and mentorship of young physicians.