The dogmas of the quiet past are inadequate to the stormy present. The occasion is piled high with difficulty, and we must rise with the occasion. As our case is new, so we must think anew and act anew. Abraham Lincoln, 1862 When I came across this quote, it made me recall my first participation at an international meeting on bone marrow transplantation, at a time when this was the only term that was used to describe the field. During a particular session there was a presentation on the use of peripheral blood as the sole source of stem cells for transplantation, and a member of the audience rose to state that it was medically unethical to consider such treatment, as it certainly could not contain stem cells. Now nearly twenty years later, peripheral blood is the predominant source of stem cells used for hematopoietic stem cell transplantation. In the same period of time there have been several other dogmatic opinions, which permeate all of medicine, that have come and gone in the field of hematopoietic stem cell transplantation, and will continue to do so with advancements from basic and clinical research. It is within this context that the format of this book was devised. Traditionally reviews on specific topics related to hematopoietic stem cell transplantation reflect the views of a single author or a research group.