A stem cell is essentially an undecided cell. It has the ability to develop into a one cell, a brain cell, or even skin cell, depending on how it ends up differentiating, or developing. The use of stem cells in therapy is so intriguing because of how these cells have the ability to morph into the kind of tissue that an individual is lacking or one that is in need of repair. These stem cells can come from a five-to-six-day-old embryo, from embryonic germ cells that ultimately produce gametes, or in the form of adult stems cells that are undifferentiated cells found within the average human body. These stem cells, and research concerning them, have given way to cell therapy—or the use of these undifferentiated stem cells to help treat a wide variety of conditions, from cancer to aging skin.