Fabric Block is the vision for the IP Center for Research Excel- lence in Health Systems and Biomedical Engineering, situated within the citadel of Knowledge of Paris Saclay. The design centers on the "cell" concept, represented by the single labo- ratory unit, where each cell forms the building's modular foun- dation, connected by corridors into an expandable, mat-like structure. The external facade acts as a 'section’ of the build- ing's virtually infinite fabric at the site boundaries, reflecting the building's internal organization. In contrast, the internal facade retracts modularly, creating a boulevard with terrac- es enhancing urban connectivity. This modular approach in- tegrates a city within a building, balancing structural perma- nence with flexible infill, creating a cohesive urban fabric.