Techniques to correct defective genes in 'non-reproductive' cells are already at various stages of clinical development and promise to be a powerful approach for many human diseases which don't yet have an effective treatment. However, altering genes in human embryos can have unpredictable effects on future generations. Furthermore the study by Huang et al showed that the although the CRISPR/Cas9 technique they used can work in the embryo, it can miss the target in the gene and is too inefficient.