Do you know any kids who have diabetes? Living with the disease can mean having to prick your finger to test your blood and getting insulin shots to keep the disease from becoming even more serious.

Maybe you know an adult with Parkinson's disease, a brain disorder that causes shakiness and stiffness, and makes it hard to walk -- symptoms that get worse over time. Actor Michael J. Fox, former boxer Muhammad Ali and former attorney general Janet Reno are among the 1.5 million Americans with Parkinson's disease. Or maybe you know of someone who can't walk because of an accident, such as "Superman" actor Christopher Reeve, who died this week.

Cures for these and other diseases, many scientists now believe, could come from research into human embryonic stem cells. Embryos are created when a male's sperm fertilizes a female's egg. The stem cells in days-old embryos can develop into almost any kind of tissue -- brain, muscle, eyes -- leading to the hope that the cells could repair injured organs and cure disease.

It's a bit like the ability kids have to learn a language more easily than adults do. These embryonic cells can "learn" just about any job they need to do, scientists think.

If they morphed into cells that make insulin, they could cure diabetes. They might replace muscle injured in a heart attack or regrow nerves damaged by accidents. Many hope they will lead to a cure for Alzheimer's disease, which can cause an older person to become confused and lose his memory. (That breakthrough is not likely to come soon, scientists say, since Alzheimer's involves the loss of many kinds of brain cells.)

What do stem cells have to do with the election? There's a big debate over whether research on them is a good idea and whether the government should pay for it. The debate centers on whether the embryos used in stem cell research are human beings.

Normally, an embryo grows into a baby in its mother's womb. In doing their research, scientists take a few stem cells from very young embryos and grow them into colonies, called stem cell "lines." The process destroys the embryo.

Some people, including some religious groups, say embryonic stem cell research should be banned because it ends a human life. They say it's not up to scientists or the government to decide which life is more important: the embryo or the patients who could be helped.

Others think that these five-day-old cell clusters -- no bigger than the dot on an "i" on this page -- are not yet fully human. It's better to use these embryos to help others, they argue. Generally, only embryos in medical clinics that are not going to become babies are used in this research.

In a kind of compromise, President Bush announced three years ago that government money could be used for stem cell research, but only on cell lines created before his Aug. 9, 2001, announcement. This would not hurt the research, he said, because there were more than 60 lines available; he promised $100 million per year in federal funds to work on them.

But scientists say that the restrictions have severely held them back, and that only 22 cell lines have turned out to be useful. They want to use new techniques to make better lines but can't get federal money to do it, they say. So far, the government has awarded about $35 million for human embryonic stem cell research.

-- Fern Shen

* In August 2001 allowed first federal spending on human embryonic stem cell research, but only on cell "lines" then in existence.

* Says stem cell research "offers both great promise and great peril, so I have decided we must proceed with great care."

* Would loosen Bush's restrictions and increase annual funding to $100 million.

* Says the president's policy has slowed progress toward scientific breakthroughs that could help sick and injured people.

THE BACK-AND-FORTH

* The president supports research on adult stem cells, which are found in the bone marrow, fat and skin of grown-ups. Groups opposed to embryonic stem cell research say scientists should focus more on these cells, because the research does not involving destroying embryos.

Kerry also supports adult stem cell research, but notes that a majority of scientists say embryonic stem cells have much more potential to lead to cures.

BUSH AND KERRY ON . . . STEM CELLS