Assuming gene editing in humans proves to be safe and effective, it might seem logical, even preferable, to correct disease-causing mutations at the earliest possible stage of life, before harmful genes begin causing serious problems. Yet once it becomes possible to transform an embryo's mutated genes into "normal" ones, there will certainly be temptations to upgrade normal genes to superior versions. Should we begin editing genes in unborn children to lower their lifetime risk of heart disease or cancer? What about giving unborn children beneficial features, like greater strength and increased mental abilities, or changing physical characteristics, like eye and hair color? The pursuit for perfection seems almost natural to human nature, but if we start down this slippery slope, we may not like where we end up.