This work deals with the socialization of labor as viewed through the prism of professional learning. It endeavors to report on the sociogenesis of workers' collectives and categories of membership by questioning the methods through which professional knowledge is acquired. The issue deals more specifically with the relationship between experiential learning and the dynamics of membership to workers' organizations. This form of reflection relies on an analysis of the phenomena of imitation and individuation. To this end, our work makes use of data collected from two fields of research: a large aeronautics corporation in a suburb of Paris, France, and metallurgical plants in Liège, Belgium. It develops a comparative analysis of these two types of socialization of labor from the points of view of the use of professional writing, the process of transmission of knowledge, experimentation, the rationalization of work and the specific influence of frames of experience.