In December 1998, two groups of scientists announced that they had successfully isolated and cultured human pluripotent stem cells. This news was greeted with both tremendous enthusiasm and concern. Because these cells can develop into most types of cells or tissues in the human body, they hold great promise for scientific research and medical advances. For example, stem cells can potentially be used to:

• Generate cells and tissues for transplantation and therapy for conditions such as Parkinson’s disease, spinal cord injury, stroke, burns, heart disease, diabetes, and arthritis;

• Improve scientists’ understanding of the complex events that occur during normal human development, as well as the abnormal events which cause conditions such as birth defects and cancer; and

• Substantially change the development and testing of drugs. New medications could be tested initially on stem cells, and only drugs which were safe and effective on the cells would be tested further on laboratory animals and humans.