The human body is comprised of millions of different cells. Each system in the body is comprised of cells that are specific to its function. For instance, muscles are made up of muscle cells, the heart is made up of heart cells, and the liver of liver cells. But how did these cells know how to become muscle cells, heart cells, or liver cells? Before they developed (differentiated) into these specific types of cells, they were stem cells (see figure 1).

Stem cells can develop into many different types of cells; a blank slate if you will. These cells are able to divide over and over and can become another type of cell (muscle, heart, liver, etc.) or they can remain stem cells (see figure 2). Because of this unique capability, stem cells are being studied to learn more about how they can repair the body or generate new organs and tissues in place of those that have been diseased or destroyed (see figure 3). Successful research into the capabilities of these cells could have a large impact on the treatment of numerous diseases and disorders; including heart disease, the leading cause of death in the United States.