President George W. Bush used his veto power for the first time on July 19, stopping a bill that would have increased federal funding for research on embryonic stem cells (ESCs). The cells might provide cures for diseases ranging from Alzheimer's to diabetes. ESCs are thought to have more disease-treating potential than similar cells found in adults, but they are controversial because harvesting them destroys a human embryo. The federal government supports research on several ESC cultures derived prior to 2001 from embryos created during in vitro fertilization (IVF) but not used. But the government won't pay to expand the research to other cell lines, which many scientists urge. Bush and other conservatives say morality forbids destroying additional embryos, regardless of the cells' treatment-producing potential. But ESC-research supporters argue the cells' life-saving potential outweighs qualms over destruction of IVF embryos, most of which eventually will be discarded.