"The roots represent at least half, by mass, of the body of a plant; through this hidden part, water and nutrients are assimilated, and together with atmospheric CO2, constitute the basis of the entire reserve food of the planet. Moreover, the roots affect plant growth through many other processes in addition to their role in water and nutrients uptake: located at the interface between soil and above-ground part, the root system plays a crucial role in anchoring and reacting to biotic and abiotic stresses. Furthermore, stress events at the root level induce the synthesis of signalling molecules (biologically or chemically active volatile compounds: BVOC or VOC) that allow the communication between plants and other organisms. These compounds are also essential for the indirect defence of plants since they are perceived as ""cry for help"" from beneficial organisms in the trophic chain, plant-herbivore-carnivore.Despite its crucial importance for the development of the whole plant, the root system has not yet been adequately investigated. In particular, very few information can be found in the literature, on the interaction between the underground and aboveground part of the plant. How do roots and shoots communicate? how do they exchange the essential information to adapt and survive stress situations? The multidisciplinary approach of the proposal provides the possibility, unexplored so far, of facing such topic.This proposal is based on the solid evidences that roots affect the overall plant growth by processes beyond the functions of supplying water and nutrients. Critical experiments indicate that root system signals modulate shoot growth and activity. We relate these findings to a postulated role of root tips as determinants of root architecture and subsequent function. Breakthroughs are targeted by this proposal focusing on the role of roots."