Stem cells are cells that have not yet differentiated into a specific type of cell. Several types of stem cells with different characteristics are currently available for use in the medical field.
Because stem cells have not differentiated yet, they have the potential to become different types of cells in the body. The most versatile is the embryonic stem cell, which is taken from an embryo about 5 to 7 days old. Embryonic stem cells can become any type of cell in the body. Adult stem cells, also called somatic stem cells, have a limited ability to change into different cells of the body. Another type, the induced pluripotent stem cell, is made in a lab but originates from cells such as skin cells in a person's own body. Scientists then "reprogram" the cell, changing it into an undifferentiated form. These cells then can become almost any other cell in the body.