While the genome editing tool CRISPR/Cas9, developed in 2012, cuts a mutation out of a gene and replaces it with a gene-piece, a newer type of CRISPR, called base-editing, can repair a mutation without cutting the DNA. Therefore, genome editing using base-editor is considered safer. Scientists from the research groups of Hans Clevers (Hubrecht Institute) and Jeffrey Beekman (UMC Utrecht) show for the first time that this base-editing can safely cure cystic fibrosis in stem cells derived from patients. The results of this study were published in Cell Stem Cell on the 20th of February.