Farming Systems Research has three core characteristics: it builds on systems thinking, it depends on the close collaboration between social and biophysical sciences, and it relies on participation to build co-learning processes. Farming Systems Research posits that to contribute towards sustainable rural development, both interdisciplinary collaborations and local actor engagement are needed. Together, they allow for changes in understanding and changes in practices. This book gives an overview of the insights generated in 20 years of Farming Systems Research. It retraces the emergence and development of Farming Systems Research in Europe, summarises the state-of-the-art for key areas, and provides an outlook on new explorations, especially those tackling the dynamic nature of farming systems and their interaction with the natural environment and the context of action.