The main contribution of this paper for social studies of scientific practice is to use and further elaborate the concept of experimental system. It is expanded from mere epistemic concerns to also incorporate the built-in practicality and societal relevance of scientific research. For this, an analysis of object construction by a potato-biotechnology research group is presented. The group's object of activity is conceptualized as a dual one comprising both the epistemic and applied objectives. The application object points to the virus-resistant cultivated potato under construction, the epistemic object to the knowledge on the virus-resistance mechanism. Two major phases of the group's work are perceived as distinct experimental systems. The transition between them is analysed in terms of a gradual evolution characterised by network collaboration, ad hoc improvization, resistance, opportunism and informal interaction.