Researchers at the CEA, the University Joseph Fourier and CNRS have developed a new approach combining protein crystallography and biomimetic chemistry to observe all the key stages of a process essential to life, the activation of the oxygen. For this, they created an artificial metalloenzyme - a complex consisting of a chemical catalyst and a protein - and observed it by X-ray crystallography on a beamline of the European Synchrotron Radiation Facility (ESRF). These results are an essential step for the development of artificial metalloenzymes capable of producing, efficiently and at lower cost, many molecules of industrial interest. In doing so, they open up new prospects for green chemistry.