KHematopoetyczna stem cell gives rise to many types of blood cells and is one of the better -characterized stem cells in the human body. It is suggested that stem cells derived from bone marrow are capable of giving rise to multiple cell types , including neural cells , skeletal muscle , cardiac muscle , liver cells , intestinal epithelial , skin, lung and kidney . Most positive marker for human hematopoietic stem and progenitor cells is the CD34 antigen . Chemically, it is a sialomucin CD34 ? transmembrane glycoprotein. There are two alternative forms: full and abbreviated as a result of alternative mRNA splicing mechanism of CD34 . It is suggested that CD34 plays a role in adhesion to the bone marrow stromal microenvironment . CD34 is expressed on the surface of the endothelium of small blood vessels . CD34 mRNA was also detected among others in liver, spleen and thymus . Contrary to current dogma , CD34 is expressed on mature mast cells . In human peripheral blood monocyte fractions are present in cells called fibrocytes that is characterized inter alia the presence of CD34 antigen . In this paper presents the latest results of research on molecules CD34 and CD34 positive cells