Acute myocardial infarction (AMI) is one of the most significant causes of morbidity and mortalityworldwide. Stem cells represent an enormous chance to rebuild damaged heart tissue. Correct definition ofthe cardiac progenitors is necessary to understand heart development, and would pave the way for the use ofcardiac progenitors in the treatment of heart disease. Identifying, purifying and differentiating native cardiacprogenitor cells are indispensable if we are to overcome congenital and adult cardiac diseases. To understandtheir functions, physiology and action, cells are tested in animal models, and then in clinical trials. But becauseclinical trials yield variable results, questions about proper cardiac stem cells remain unanswered. Transplantedstem cells release soluble factors, acting in a paracrine fashion, which contributes to cardiac regeneration.Cytokines and growth factors have cytoprotective and neovascularizing functions, and may activate residentcardiac stem cells. Understanding all these mechanisms is crucial to overcoming heart diseases.