The cells called stem cells or germinal cells are capable to multiply and transform (differentiate) to specific type of mature (differentiated) cells. Afterwards the mature cells can carry out their function in the organism.

          In some tissues, like for instance skin and mucus, the partly differentiated stem cells occur for the whole life. These stem cells constantly multiply and develop into mature cells and thus renew the aforementioned tissues (e.g. skin and mucus), the cells of which quickly die and peel off. Also haematopoietic stem cells are the kind of stem cells that constantly renew red blood cells, white blood cells and platelets. Some germinal cells occur only during the human embryonic life and after fulfilling their role they disappear. Some germinal cells differ from others by their maturity. Immature germinal cell can develop into various types of cells, more mature cells are able to transform only into certain types of cells (e. g. skin germinal cells can give rise only to skin cells).

In umbilical cord blood the stem cells are probably able to give rise to almost every human cell occur. Moreover, they are young, and compared to the cells of adults, they have full growing capacity.