Stem cells are multipotent cells arise from the bone marrow, which have the ability to self-regenerate and differentiate into any form of cell in human body, like osteocytes, myocytes, hematopoietic and some other cells. Hematopoietic stem cells are adult stem cells that give rise to all blood cells including leukocytes, erythrocytes and platelets. Hematopoietic stem cells can be obtained from three sites, bone marrow, peripheral blood and cord blood. Bone marrow is the most common procedure as it gives high numbers of stem cells but it also has some disadvantages. Peripheral blood is becoming widely used as it is an easier approach for the donor, this is done by giving granulocyte colony stimulating factor ‘GCSF’ which is a glycoprotein work as mobilizer to induce the mobilization of hematopoietic stem cells from the bone marrow into the peripheral blood. Collecting stem cells from umbilical cord blood is the most recent source and it is very promising for future use. Bone marrow transplantation or hematopoietic stem cells transplantation is the fundamental method used to cure many malignancies and blood disorders, such as: leukemia, thalassemia, sickle cell disease and so on. The therapy demands high preparing programs of nursing and medical maintenance for several weeks of exhausting regimen: specific diet and chemotherapy dosage or radiation to prepare the patient for the transplant.