We have found medical providers who match your requirements, please select up to 5 countries and click GO for further information. A bone marrow or stem cell transplant is where abnormal stem cells from a person's bone marrow are destroyed and replaced with healthy stem cells, either from that person or from a donor. The bone marrow is a spongy substance in the center of most bones. Your bone marrow contains stem cells that mature and into three types of cells; white and red blood cells and platelets.