Researchers at Massachusetts General Hospital say they have extracted stem cells from human ovaries and made them generate egg cells. The advance, if confirmed, might provide a new source of eggs for treating infertility, though scientists say it is far too early to tell if the work holds such promise.

Women are born with a complement of egg cells that must last throughout life. The ability to isolate stem cells from which eggs could be cultivated would help not only with fertility but also with biologists’ understanding of how drugs and nutrition affect the egg cells.