To understand why some cancer cells resist radiotherapy, an international team of researchers has used crystallography to “photograph” the first moments of the molecular ballet that allows these cells to repair their DNA. The study involved teams from the CEA, CNRS, PROXIMA-1 beamline at SOLEIL, University of Paris-Sud, Gustave Roussy, Aix-Marseille University and University Paul Sabatier—Toulouse III. It was published in Nature Structural & Molecular Biology.