INTRODUCTION
To understand adult stem cells, it is important to first understand what a stem cell is not. All the cells of the body, called somatic cells, are specialized cells that do one specific thing; they will never do anything else, and they do not proliferate. For example, a skin cell will never be anything other than a skin cell and it will never divide. It will do what a skin cell does until the day it dies. It is the same for brain cells that respond to electrical impulses, pancreatic cells that make insulin, muscle cells that contract, and all the other cells of the body that do… what they do.