A new piece in The New York Times Magazine looks at the growing controversy surrounding three-parent fertilization. The procedure introduces a donor's cytoplasm into the mother's egg, potentially adding a third parent's genetic data to the child, but effectively treating mitochondrial disorders and a range of infertility issues. As the science develops, it's also become the center of a heated battle around genetic ethics. Three-parent IVF is the first technique to alters the germ line, disrupting the natural flow of genetic information from parent to child. As a result, many are already casting it as the first step towards genetic engineering. Three-parent fertilization already works as medicine, and could make a huge difference for the millions of women struggling to conceive, but ethical questions are still holding it back. Now that we have the power, should we use it?