My interest in blood stem cells and cord blood dates back to my fellowship in Pediatric Hematology/Oncology at Duke. During my fellowship, I worked on the development of novel antileukemia drugs based on analogs of purine metabolism and treated a teenage patient with refractory T‐cell acute lymphoblastic leukemia with a novel anti‐leukemia drug, 2′‐deoxycoformycin, an inhibiter of adenosine deaminase. During 5‐day course of therapy, his leukemia converted from a T‐lymphoid to a myeloid phenotype before our eyes 1. I subsequently established a cell line from these leukemic cells, DU‐528 and, ultimately, proved that this leukemia arose from a common lymphoid‐myeloid progenitor cell 2, which then led me to the study of hematopoietic stem and progenitor cells. Hal Broxmeyer, who would go on to become a pioneer in the use of cord blood as a source of donor cells for bone marrow reconstitution, mentored me as I studied normal and malignant hematopoietic stem cells isolated from bone marrow, fetal liver, and umbilical cord blood. In the clinic, I cared for children with leukemias and blood dyscrasias, including a young boy named Matthew Farrow from Salisbury, NC, with Fanconi anemia (FA) and evolving bone marrow failure. This genetic disease, which arises from a mutation in genes that encode the enzymes responsible for DNA repair, is associated with a host of serious medical and developmental problems. The prognosis for Matthew's condition was stark: most children with Fanconi anemia died of bone marrow failure or leukemia in the first decade of life, unless treated with a bone marrow transplant from a human leukocyte antigen (HLA)‐matched donor.