Adult humans fail to regenerate their hearts following injury, and this failure to regenerate myocardium is a leading cause of heart failure and death worldwide. Although all adult mammals appear to lack significant cardiac regeneration potential, some vertebrates can regenerate myocardium throughout life.The mechanism of pathological myocardial growth involves myocyte hypertrophy and proliferation. However, the origin of replicating myocytes in the human heart remains to be identified. The major challenging question is whether the myocardium possesses a subpopulation of myocytes that are not terminally differentiated or whether primitive cells reside in the heart and undergo lineage commitment generating amplifying cells. The possibility is advanced that cells expressing surface antigens commonly found in stem cells are stored in the adult heart and, following stimulation, can give rise to myocytes and vascular structures. Thus, the damaged heart has the potential to repair itself.Stem cells are defined as clonogenic cells that are capable of self-renewal and multilineage differentiation. Stem cells give rise to progenitors that lose self-renewal properties, forming progeny with much more limited differentiating potential. The ultimate fate of progeny is the generation of functionally competent mature cells. This model of cell growth applies to all self-renewing organs