DIANE DAVIS, CNN VIEWER: My name is Diane Davis, from Albany, New York. And I want to "Ask CNN" what exactly are stem cell lines and what are they used for?</s>ELIZABETH COHEN, CNN MEDICAL CORRESPONDENT: Stem cells come from leftover embryos that are sitting in fertility clinics, the parents no longer want, to start a pregnancy. You take an embryo, you let grow to until it's about five days old and it becomes a blastocyst. You then scoop out the stem cells from inside that blastocyst and allow them to multiply. They can multiply indefinitely for years and years and you can get millions upon millions of stem cells. One embryo could create millions of stem cells, but they would all be part of one stem cell line. Now, the reason why stem cell research is potentially so exciting is that these cells, researchers think, can be turned into basically any type of human tissue and they hope, any type of organ. So for example, you may be able to grow a liver out of stem cells, and then that liver could be used for someone who needs a liver in a transplant. So researchers hope that stem cells can be used to cure and treat all sorts of diseases.
"Ask CNN": What Are Stem Cell Lines and What Are They Used For?