70 years ago, the ordinances promulgating the fields of application of Social Security were voted by the provisional government of the Republic. An old, secular dream emanating from people wanting to live without the anxiety of the next day finally saw the light of day. The main builder of this most humanist building was called Ambroise Croizat. Who knows him today? 70 years later, it is time to tell this beautiful story of "secu". Where does it come from, how did it become possible, what are its basic principles, who are its builders and what has become of it over the decades? In the end, there will be a parallel portrait of a man, the story of a long struggle for dignity and the portrait of an institution embodied by its everyday actors.