The environment and the individual do not constitute separate entities, isolated from - and forced to coexist with - one another. Instead, they are two elements that evolvejointly in a search for balance. These general considerations about the human condition apply to the world of work. The elements of the work environment are major determinants of the activity of the individuals involved. They are also targets, in the sense that the environment is an object of transformation for the individual. Within these determinants, organizations have, over the past few years, been the subject of much attention on the part of ergonomists, since it remains a source of influence and a major target for the activity. Because of this, organizations have become an object of study and transformation for ergonomists. To specify, this text will argue that ergonomie action can be viewed, on the one hand, as a transformation of the organization, and on the other hand, as an opportunity to influence the development of individuals. In more concrete terms, in this chapter we will describe the course of an ergonomie intervention, its results and the reflections it led to. Over the course of this intervention, which was centred around an organi­ zational change, we had the opportunity to set up an 'experimentation' that allowed us to solve the actual problems of work and to construct the forms of collaboration that were necessary to solving these problems. This allowed us to identify sorne essential features in order to structure a system for the ergonomie intervention. We organized this system around moments where it was possible to define the rules of operation of work, and moments where more space was left for the development of individ­ ual and collective experience. This last point allows us to liken our method to an 'intrinsic approach' (Rabardel and Béguin, 2005)- an approach that is consistent with the personal points of view of the persons that make up the situation, that is, the workers themselves. This element seems crucial to us, since it allows individuals undergoing a process of organizational transition that is synonymous with cognitive and social disruptions to construct their own spaces for learning. By working on finding solutions to everyday difficulties related to their work, and attempting to construct a system that is as effective as possible for dealing with these problems, workers construct new representations of their current and future work. This allows us to open up two paths for reflection: • On the one hand, the running of the organization must be part of a developmental process, by allowing a joint evolution of the organi­ zational structure and of human activities. • On the other hand, an ergonomie intervention in organizational design may take place as part of this process