 Welcome to the IHES on behalf of the Organizing Committee. It's a great pleasure of opening this conference in honor of Ofer Gabber on the occasion of his 60th birthday. This is one of the four events celebrating the 60th anniversary of the creation of the IHES. So happy birthday, Ofer. I will speak about Ofer Thursday at the party, but for a moment, let me just say this. Ofer has generously helped many of us in different ways, sometimes by suggestion, an idea, a new viewpoint or perspective, sometimes by the poof of the crucial result, key lemma, sometimes by pointing out an inaccuracy or mistake, and usually showing how to correct it. And also sometimes by confirming the validity of a result, which is certainly the best certification one can dream of. So today, I'm happy that through this conference, we can express our gratitude to him. I would like to thank the institutions that sponsored this event, Clay Mathematics Institute, Foundation Mathematics Academy, CNRS, and of course the IHES, which in addition to its financial support provided us with its usual elaborate technical assistance and special thanks to Elisabeth Jassrand for her dedication to her task.