I am a undergraduate student of engineering and I'm planning to go for Master's in physics department. I've watched some websites of research faculty or groups and I think (correct me if I'm wrong ;) there are main theoretical and experimental fields of these: - Elementary particles - Condensed matter - Non-linear or non-equilibrium systems/complex systems/biophysics I don't quite understand what the last field(Non-linear or non-equilibrium systems/complex systems/biophysics) is about... I know that there are some researches in this field about complex systems of molecular level or bigger (i guess mainly biophysics?) but as i know of, there are also researches about quantum level of non-equilibrium or complex systems... And there are researches about complex systems in fields of condensed matter like complex systems like many-body problem, strongly correlated systems, etc... So, what is field of complex systems physics about? and what are main differences between condensed matter physics and complex systems physics fields? Thank you!