Agroecology is essentially based on the use of biodiversity and ecosystem services in agriculture production, and thus represents a true rupture with the way agriculture has been seen and analyzed by mainstream science for over a century. AE does not have a consensual definition, but it represents a new conceptual space in which to think about agriculture sustainability through strong interactions between science and society with a wealth of new concepts, questions and tools. Among the diverse "incarnations" of AE, the lowest common denominator is found at plot level. The basic and common principle is to enhance the services provided by living organisms, taking the optimal advantage of natural resources, especially those which are abundant and free (sun radiation, air carbon and nitrogen, rainfall). AE aims to increase production in a sustainable and resilient way that will maintain and improve the ecosystem capital in the long term. It will pilot functional biodiversity above and underground, over space and in time, by both intensifying biological cycles for nutrients, water and energy, and controlling aggressors of crops. Because ecosystem services are involved, A E has long been working on larger scales (farms, landscapes, watershed basins, value chains, food systems). It has been extremely interested in inter-disciplinary research questions, in particular about some of the drivers of agriculture evolution such as food industries and distribution, consumer health, public policies, etc. Furthermore, since AE strongly depends on locally available natural resources including agro-biodiversity, it does not prescribe ready-to-use technical packages to farmers. The models and solutions are built mingling scientific and traditional knowledge and strongly relying on local learning and innovation processes. With the many challenges ahead, AE represents a true alternative for agriculture transformation but it questions the role and practices of agriculture research and cal