Hematopoietic stem cell transplantation (HSCT) involves replacing a patient's bone marrow with healthy stem cells from a donor. The document provides an overview of HSCT, including its history, types of transplants, the transplant process, and potential complications. It discusses how stem cells are collected from bone marrow, peripheral blood, or umbilical cord blood and cryopreserved. The transplant process includes conditioning chemotherapy/radiation, stem cell infusion, and recovery. Complications can include graft-versus-host disease and infection. Careful donor matching and screening is important for transplant success.