Over the last few decades, researchers have developed innovative techniques for altering genetic sequences. More recently, scientific breakthroughs have greatly reduced the cost and complexity of making highly targeted changes in living cells. There is consensus among experts that these advances could have wide-ranging clinical applications. Although the advances may have the potential to prevent or even cure a variety of diseases when used in adults, children, and even fetuses or gametes, they also raise many important ethical and societal questions.