The U.S. government is creating a master list to show which embryonic stems cells qualify for taxpayer-funded research.
The rules said that in order to qualify, cells must be from fertility clinics that would otherwise throw the embryos away.
The embryos must also come with documentation that proves the donor gave full consent and was aware of other options like donating to infertile woman.
But critics fear the rules will disqualify hundreds of existing stem cell lines that do not have that documentation.
Earlier this year President Obama lifted restrictions on using government funds for embryonic stem cell research.