A blood and marrow stem cell transplant is a procedure that replaces a person's faulty stem cells with healthy ones. Stem cells are found in bone marrow, a spongy tissue inside the bones. Stem cells develop into the three types of blood cells that the body needs: Red blood cells, which carry oxygen throughout the body - White blood cells, which fight infections and Platelets (PLATE-lets), which help the blood clot. The. purpose of the community is to share support and information with Stem Cell Transplant patients and their loved ones. Topics in the community include: causes, clinical trials, complications, family issues, living with a Stem Cell Transplant, prognosis, research, surgery, treatments