Muse cells are non-tumorigenic reparative endogenous stem cells identified by SSEA-3+. They are pluripotent and are stably mobilized from the bone marrow to the peripheral blood and distribute to organ connective tissue, where they contribute to daily minute repair of damaged/lost cells by spontaneous differentiation into tissue-constituent cells. Muse cells specifically home to damaged site to repair the tissue by simultaneous differentiation into multiple tissue-constituent cells. When the number of endogenous Muse cells is not sufficient, administration of exogenous Muse cells delivers robust functional recovery. Muse cells do not need to be "induced" or genetically manipulated. Intravenous drip is the main method of administration, making surgical operation unnecessary. Because Muse cells have an immunomodulatory system similar to the placenta, donor-derived Muse cells can be directly administered to patients without HLA-matching or immunosuppression therapy. Allogeneic Muse cells remain in the host tissue as differentiated cells for more than half a year. Clinical trials for the treatment of myocardial infarction, stroke and epidermolysis bullosa with intravenous injection of donor-derived Muse cells are currently conducted by the Life Science Institute Inc. Muse cells may safely provide clinically relevant effects compatible with the 'body's natural repair systems' by a simple cost-effective strategy.