The study by Schwank et al. provided the proof-of-concept by using the CRISPR/Cas9 genome editing system to correct the Cystic Fibrosis Transmembrane Conductor Receptor (CFTR) locus by homologous recombination in cultured intestinal stem cells of cystic fibrosis patients, and the corrected allele is expressed and fully functional as measured in clonally expanded organoids [13]. The gene discussed is CFTR; the disease is cystic fibrosis.