This paper develops a longitudinal case study of the development of the Italian corporate law sub-field. This operates as a distinct space within the broader Italian legal field, having formed in the aftermath of the process of Europeanization and the creation of the Single Market. In this context, we advance understanding of sub-fields and how they develop through the concept of field partitioning. We define field partitioning as a process whereby an established field develops a sub-field(s) with its own distinctive logics and institutional infrastructure. We theorize (see figure 2) field partitioning as a multi-stage process involving the following mechanisms: focusing on new opportunities; inter- and intra-subfield networking; and distinction and show how each contributes respectively to the emergence, development and consolidation of a sub-field. We also identify the conditions of resource dependency binding the sub-field to its parent field; these dependencies explain why we may have the development of a sub-field rather than of an altogether new field.