In highly controversial research that some view as crossing an ethical line, Chinese scientists have edited the genomes of human embryos, Nature reports. The study, published online in the journal Protein & Cell, details how the researchers used the genome-editing technology CRISPR-Cas9 on “non-viable” embryos in an attempt to alter the gene responsible for a potentially lethal blood disorder. After encountering obstacles with the technique and “off-target” mutations, the team stopped the process. About a month ago, rumors of the research swirled, stirring calls by some for a moratorium on such genetic engineering of human embryos.