DON REED HAS a favor to ask. His son Roman has been in a wheelchair ever since he was paralyzed in a football accident 10 years ago. Right now modern medicine offers no hope.

But some day, doctors and scientists have told the Reeds, there may be a way to help Roman. It involves microscopic human cells known as stem cells, which have an unusual ability to replicate and could theoretically replace any damaged or diseased tissue in the human body. Visiting a UC Irvine lab in March 2002, Don Reed even held a rat that had been paralyzed but was able to crawl after receiving an experimental stem-cell therapy.

The problem is, the Bush administration has refused to grant federal funding for most research on cells taken from human embryos, which are thought to hold the most potential. So thousands of desperate and infuriated families like the Reeds are intent on finding more money for that research. They say we could soon have a cure for juvenile diabetes, therapy for heart disease and Parkinson's, even possibly a way to...