Subjecting a heterogeneous cell population (one with both stem cells and non-stem cells) to extreme stress selectively eliminated the non-stem cells and resulted in the enrichment of stem cells in the population. The stress can take many forms, including without limitation, cell toxins, high temperature, high salt, and low oxygen (hypoxic) conditions. The number of stem cells remaining after stress were increased, and showed increased expression of traditional stem cell markers. The stem cells were shown to be capable of proliferation and differentiation into multiple types of cells. This method allows purification of stem cells from adult heterogeneous cell populations on a large scale basis without requirement of expensive equipment, and without requiring the presence of cell surface markers. Stem cells produced by the above method can be used for clinical applications, including tissue engineering.