Stem cells have two important characteristics that distinguish them from other types of cells. First, they are unspecialized cells that renew themselves for long periods through cell division. The second is that under certain physiologic or experimental conditions, stem cells can be induced to become cells with special functions such as the beating cells of the heart muscle in a person with a heart problem, a neuron cell in the brain of a person with parkinson's disease, a nerve cell in an injured spinal cord, a bladder cell in the bladder sphincter of a person with a weak bladder, or the insulin-producing cells of the damaged pancreas of a diabetic person. As shown in the image above, the stem cell does this by repeatedly splitting into one stem cell and one specialized cell -- instead of splitting into two stem cells.

Here are examples of successful stem cell treatments around the world:

Paralyzed woman walks again after stem cell therapy. Nov 27,2004 (The Korea Times) - A team of Korean researchers claimed Thursday they had performed a miracle by enabling a patient, who could not even stand up for the last 19 years, to walk with stem cell therapy. During a press conference, the scientists said they had last month transplanted multi-potent stem cells from umbilical cord blood to the 37-year-old female patient suffering from a spinal cord injury and she can now walk on her own. The team was co-headed by Chosun University professor Song Chang-hun, Seoul National University professor Kang Kyung-sun and Han Hoon, Ph.D, from the Seoul Cord Blood Bank (SCB). 16:30 29 November 04: The New Scientist reports that Austrian scientists have demonstrated a stem cell treatment to regenerate age-weakened bladder muscles. Stem cells were taken from the patients, cultured, and injected into the bladder sphincter. "Within 24 hours, 90% of the women had no urinary leakage. After two weeks, both doctor and patient could a see a marked increase in muscle tissue and contraction power under the ultrasound. Now, more than a later year, 18 of the 20 women have maintained full control over their bladders ... The team is currently treating eight to 10 women per week and long waiting lists are building up."

Stem cell treatment allows paralyzed Brazilian to walk, talk again
Channel News Asia Nov 20, RIO DE JANEIRO (AFP) - A Brazilian woman who suffered a brain hemorrhage that left her paralyzed on one side and unable to speak has regained her ability to walk and talk after undergoing a stem cell transplant, hospital officials said. Doctors injected the stem cells into the brain of Maria da Graca Pomeceno, 54, five days after a brain hemorrhage left her a hemiplegic. The cells were extracted from bone marrow in her pelvis.

First Patient to Get Stem Cell Treatment for Crohn's in Remission
WebMD Medical News Aug. 10, 2001 -- Joy Weiss treated herself to a Big Mac for lunch on Friday and then considered whether she should top off the meal with a salad, some fruit, or both. For most 20-somethings, that doesn't sound like an extraordinary lunch choice, but for Weiss it's a miracle meal.
The miracle in this case is a controversial, experimental medical procedure that involves stem cells harvested from a patient's own bone marrow.
Ten weeks ago, Weiss became the first person to undergo the stem cell infusion for treatment of Crohn's disease, a condition in which the body's immune system attacks the patient's digestive tract. On Monday, researchers at Chicago's Northwestern Memorial Hospital completed a second such treatment in another Crohn's patient. The second patient, reportedly a 16-year old male, has requested anonymity, says Richard Burt, MD, lead researcher in the pilot study. Burt says, however, that the second patient is doing well.
For years, Weiss did not know a single day without pain, the gut-wrenching pain caused by Crohn's disease. "Until I was 19 I could never get my weight up above 90 pounds," says the 22-year-old Weiss. Dairy foods, salad, fruit, nuts, fried foods -- all were dietary no-no's for Weiss, who was diagnosed with Crohn's disease when she was 11.

Many details on Stem Cell research are available at U. S. National Institutes of Health Stem Cell Information Site and American Academy of Anti-Aging Medicine Stem Cell Section.