Professor David Anderson describes the types and properties of different stem cells. The most well known, embryonic stem cells, are the most flexible.
What we know about stem cells is that stem cells are primitive, undifferentiated cells that have the capacity to differentiate into specialized cell types, and they also have the capacity to make more cells like themselves, more stem cells - we call that self-renewal. So all stem cells, by definition, have to have the capacity to both self-renew and to make specialized cell types. We also know that there are different kinds of stem cells. There are stem cells that make, for example, all of the cell types in the blood and the immune system, and there are stem cells that can make all of the cell types in a particular tissue, such as the liver. But those are different from the stem cells that you hear about in the news most of the time, which are the embryonic stem cells, and those cells are the most plastic and flexible stem cells. They are thought to be able to make all the different cell types in the body.
Use of embryonic stem cells in research has been hotly debated for several years. This animation presents the basics on how stem cell lines are established. For more information on how techniques similar to this are used in research.