A STEM CELL is basically any cell that can replicate and differentiate. This means the cell can not only multiply, it can turn into different types of tissues. There are different kinds of stem cells. Most people are familiar with or have heard the term “embryonic stem cell.” These are cells from the embryonic stage that have yet to differentiate – as such, they can change into any body part at all. These are then called “pluri-potential” cells. Because they are taken from unborn or unwanted embryos, there has been considerable controversy surrounding their use. Also, while they have been used in some areas of medicine – particularly, outside the United States – they have also been associated with occasional tumor (teratoma) formations. There is work being conducted by several companies to isolate particular line of embryonic stem cells for future use.