Nearly two years after the isolation of human embryonic stem cells promised to change the face of medical research, progress is still on hold due to scientists' limited access to the cells. Private companies are restricting use of their supplies, and government initiatives to provide the cells to academics remain stalled by abortion politics.

ES cells, believed to be capable of turning into any kind of tissue, are derived from human embryos. A law prohibiting federally funded researchers from performing embryo research has left most academic scientists effectively barred from working with ES cells, although the National Institutes of Health has recommended that researchers be able to use existing ES cell lines. A bill pending in the U.S. Senate would allow researchers to derive new ones as well. Critics of the research are opposing both measures.