(CNN)Fetal tissue has been used since the 1930s for vaccine development, and more recently to help advance stem cell research and treatments for degenerative diseases such as Parkinson's disease. Researchers typically take tissue samples from a fetus that has been aborted (under conditions permitted by law) and grow cells from the tissue in Petri dishes.
Many of the uses of fetal tissue — and much of the debate — are not new. "It's just that the public is finding out about it," said Insoo Hyun, associate professor of bioethics at Case Western Reserve University.
In addition, the ways that fetal tissue are allowed to be obtained and used are not new either, Hyun said. The U.S. Department of Health and Human Services released guidelines on the topic in the 1990s.