The principle of modularization of the products and processes of production is in the heart of the reorganization of firms in the contemporary capitalism. This strategy tries to split the end product into a series of connected subsets some to the others by standardized interfaces. It allows quite at once to delegate with external suppliers the fixed asset of the capital and the risks of conception/production, to take advantage of differences of labour costs and to propose to the markets personalized products. But this strategy is conditioned in the capacity to decouple the complex product, thus in the capacity of the producers/designers of these modules to work independently each others, inside fixed interfaces. Howewer the product still uncertain, not stabilized ex ante before its conception and its production. To face this uncertainty, the producers stand-up a cooperative space in which circulate the interdependence and the indecision of the product, from the parts to the whole lot. The systematic uncertainty of the product involves the social integration of the design activity. The firm is in contradiction between the centrifugal forces stemming from the uncertainty of the product and the centripetal forces of the modularisation. The first ones try to take control of an uncertain product, the seconds to exceed the trade constraints enclosing the organization, by segmenting the productive space to establish it in competitive and transparent market. Taken in this contradiction, can the product remain technically mastered and the organization preserve its coherence? This contradiction is, according to our hypothesis, in the heart of the contemporary dynamics of capitalism and transformation of the firms.