Electron Spin Resonance (ESR) is one of the most fundamental measurement techniques in condensed matter physics. It gives valuable information on many interesting problems, by probing the electron spin dynamics directly. Steady progress in experimental techniques, especially in high fields, and synthesis of countless number of new materials set up the stage for a significant step forward in applications of ESR. However, the potential of ESR on strongly correlated systems is not yet fully realized. A large part of the reason is that the interpretation of the data is often difficult, owing to the lack of an ESR theory appropriate in the presence of strong correlation.

On the other hand, recently new theoretical approaches to ESR, such as those based on field theory or on large-scale numerical calculations, have been developed. They have enabled precise descriptions of ESR spectra in strongly correlated systems. At present, unfortunately, they are applicable only to a limited set of problems. However, based on recent developments in theory and in experiment, we can hope for major progress in the near future.

In order to stimulate such advances, we meet to discuss what is understood and what is not, in ESR of strongly correlated systems. It is encouraged to put forward questions, as well as to clarify what is understood so far.