Human embryonic stem (hES) cells, derived from blastocysts, are capable of unlimited self-renewal and
differentiation into all cell lineages of the body. Because of their pluripotent nature, hES cells are
valuable tools for understanding human development and advancing the field of regenerative medicine.
However, one key to harnessing the therapeutic power of hES cells for biomedical applications begins
with determining how these cells maintain their pluripotent and undifferentiated state.

This primer on stem cells is intended for anyone who wishes to learn more about the biological properties of stem cells, the important questions about stem cells that are the focus of scientific research, and the potential use of stem cells in research and in treating disease. The primer includes information about stem cells derived from embryonic and non-embryonic tissues. Much of the information included here is about stem cells derived from human tissues, but some studies of animal-derived stem cells are also described.

The NIH developed this primer to help readers understand the answers to questions such as:

What are stem cells?
What are the different types of stem cells, and where do they come from?
What is the potential for new medical treatments using stem cells?
What research is needed to make such treatments a reality?