Since 2001 when stem cell research first captured our nation’s attention, I’ve said many times the issue will have to be reviewed on an ongoing basis -- and not just because the science holds tremendous promise, or because it’s developing with breathtaking speed. Indeed, stem cell research presents the first major moral and ethical challenge to biomedical research in the 21st century. In this age of unprecedented discovery, challenges that arise from the nexus of advancing science and ethical considerations will come with increasing frequency. How can they not? Every day we unlock more of the mysteries of human life...