The president-elect is not known for being particularly religious, but he’s surrounding himself with traditional conservatives, including staunch pro-life policymakers like Representative Tom Price of Georgia and Vice-President-elect Mike Pence. At this point, watchers of the field can only speculate as to the Trump administration’s stance on embryonic stem cells. (His team did not return a request for comment). But some fear the new regime may halt stem-cell and fetal-tissue research, which many abortion opponents consider to be life and many scientists regard as the ingredients of breakthroughs.

At issue is the humanity of a cluster of cells that’s created during the in-vitro fertilization process. About a week after a woman’s egg is fertilized with a man’s sperm, it becomes a blastocyst, a 100-cell blob smaller than the head of a needle. After implantation, the couple might donate some of the unused blastocysts for use in stem-cell research.

For years, embryonic stem-cell research was strictly limited by a policy imposed by former President George W. Bush in 2001. “Most Americans share a belief that human life should not be reduced to a tool or a means,” Bush wrote in The New York Times that August, defending his decision. Research on embryonic stem cells was limited to the so-called “Bush lines,” a couple dozen colonies of cells that had already been cultivated. In those days, some scientists would label their lab equipment if it had been purchased with public funds and thus couldn’t touch embryonic cells. During his eight years in office, Bush vetoed bills that would have expanded funding for stem-cell research. President Barack Obama lifted the ban by executive order in 2009, allowing hundreds of new cell lines to flourish.

Embryonic stem-cells are now being tested as possible treatments for juvenile diabetes, Parkinson’s disease, and macular degeneration, among other ailments. Fetal tissue, meanwhile, has been used for studies on the Zika virus and other pathogens. Fetal research, too, has stoked controversy: In the past year several states passed laws—including one Mike Pence signed in Indiana—prohibiting the donation of fetal tissue for research. South Dakota’s law made research on fetal tissue a felony.

To Paul S. Knoepfler, a professor of biology at the Institute for Regenerative Cures at the University of California, today feels like “2006 all over again. Obama opened the door, and now we’re wondering, is the door going to be closed?”

If he is confirmed as HHS secretary, Price would oversee the National Institutes of Health, which gives grants to researchers working on embryonic stem cells and fetal tissue, along with other research areas. Price could decide to cease funding these projects, or Trump could issue an executive order reversing Obama’s policy.