[Root health: a world of complexity] A root study was undertaken at the SCRDC laboratory in an attempt to elucidate the unexpected impact of a virus which, used in the context of plant selection, helped improve the biomass potential of the species. The complexity of root systems can produce many pitfalls in such studies. Interactions at the root level are so complex that Cartesian methods do not offer suitable tools for understanding the system. However, it is possible to develop useful and efficient methods for understanding and managing this complexity. After having analyzed the knowledge acquired using Cartesian methods, it is necessary to look into synthetic methods offering the possibility of furthering academic and practical progress. The best adapted and most plastic roots in relation to their ecosystem have numerous characteristics that are probably interrelated. Hence, a global progress towards root health is a realistic objective whose success would be important at the environmental level. Genetics and management also have a role to play. To make progress in this field, it is therefore necessary to dare go off the beaten track. It is not only the difficulty of a complex issue that is in question but also the fact that our education has taught us to avoid meddling with complexity. The simplistic approach does not allow a good understanding of root heath, or even plant health, or of the relationships between the plant and its enemies, the rhizosphere and the environment. Philosophers are therefore justified in warning us against the impacts of knowledge fragmentation. The following text comes within the scope of a desire to tackle the world of roots in all of its complexity in order to avoid the traps inherent to pure Cartesian logic.