Blood stem cells refer to hematopoietic mother cells, also known as hematopoietic stem cells, with excellent self-renewal (self-renewal) and proliferation capabilities, usually found in the bone marrow, about 1% of the bone marrow with nuclear cells, in the peripheral blood 0.1%. These blood stem cells, in addition to being found in the bone marrow and peripheral blood, are also rich in the umbilical cord blood at birth. Stem cell transplantation, simply to infuse stem cells into the peripheral blood of the patient, because of its special home-and-nest function, new stem cells will replace abnormal or dysfunctional tissue, restore organ function, called stem cell transplantation.

Characteristics of blood stem cells

The percentage of blood of human body is about 7 to 8% of the body's body weight, in 60 kg of adults, about 4,200 to 4,800 c.c. blood is divided into plasma and blood cells. The plasma is slightly yellow, about 90% of which is water, and the rest is mostly plasma proteins (including many antibodies, hormones, enzymes, etc.), as well as trace amounts of nutrients, metabolic waste and gas.  
 
Blood cells can be divided into lymphatic blood cells and myelin hemies. Lymphatic blood cells, including B lymphocytes, T lymphocytes, and natural killer cells, form the body's immune system, circulate the body, hunt for foreign antigens, and produce an immune response to eliminate it. Myelin blood cells are divided into red blood cells, white blood cells and platelets, respectively, with assistance in gas transport, disease prevention, blood clotting and other functions.
Different blood cells have different life cycles, from hours to months, and the body must produce about 100 billion blood cells a day to supplement the normal aging and depletion of blood cells and achieve the normal physiological balance of the body. The production of such a large number of blood cells depends on a very small group of hematopoietic stem cells, which shows the importance and activeness of hematopoietic stem cells in the human body.  
 
Hematopoietic stem cells are cells which have the ability to re-renew themselves in the blood or bone marrow, where at least one sub-cell maintains the same characteristics as before the division and can divide continuously; Hematopoietic stem cells differentiate into a variety of specific blood cell; The ability to move from bone marrow to peripheral circulation and back to bone marrow is an important basis for hematopoietic stem cell transplantation.