It is well established that arbuscular mycorrhiza (AM) symbiotic fungi contribute to the scavenging of soil mineral nutrients in exchange for photosynthetically fixed organic carbon in the large majority of land plants. However, plants are naturally interconnected by a common mycorrhizal network (CMN), and the terms of trade as well as developmental interactions between plants connected with a shared fungal partner are still poorly understood. To facilitate the decrypting of such complex relationships, model systems allowing the study of two or more interconnected plants have been developed. Compartmented microcosms were designed to physically separate the roots of studied plants (using meshes) that can in fact only interact through a CMN the integrity of which can be controlled. Here, we report on recently published results relative to the implementation of various specifically designed microcosms to better understand the role in plant-plant relationships of the CMN and that of the AM fungal species involved.