It is my great honor and pleasure to welcome you to the CAT-2019 conference that promises to provide innumerable opportunities to network, share ideas and collaborate. Many important chemical reactions require inputs of energy to proceed. Catalysts, however, can promote these transformation by lowering the energy required to complete the reaction. It is hard to imagine the world today without the impact of catalysis on the fundamental aspects required for life, namely energy, food and water. To make a catalyst more efficient, a molecular level understanding of the catalyst material, the reaction kinetics, intermediates, active centers and pathways are important. Modern diagnosis tools, in particular operando spectroscopies and imaging techniques that are capable of capturing reaction processes at critical length and time scales, have been or are being successfully developed to advance the field of catalysis science that we will be able to learn from this conference.