To better understand the evolution of activism and activists in social and humanitarian organizations, this article examines the case study of Emmaüs in France. It seeks to retrace the three main periods and six main generations of activists since the organization’s creation : first, the era of pioneers (1953-1956), the first militants in the famous “winter of 1954” ; second, the alternative activism of the Trente Glorieuses, more social in the 1960’s, then more utopian in the 1970’s ; and finally the militancy of social and economic crisis, involving first Christians of the French “second left”, then more institutionally-oriented activists. The author also demonstrate the porosity between “domestic” and “international” humanitarism, between “social” and “humanitarian” involvement, and the transformation of “old” political and religious militancy which pass through a crisis.