Leukemia, generally refers to cancers of the WBCs. In America, more than forty thousand people are diagnosed with leukemia each year. It arises in the bone marrow, the soft, sponge-like material inside long bones of four limbs, where blood cells form. Under healthy circumstance, mature blood cells migrate from bone marrow into the blood circulatory system, but in the bone marrow of leukemia patient, some white blood cells divide too fast and cannot get mature as a result of incorrectly development, which finally crowd out the normal, healthy ones.