This journal continues Systems Science and Mathematical Sciences, which has been published since 1988. Since complex systems are currently at the forefront of systems science research, to meet the challenge of this emerging science, in 2001 the journal's profile was modified and its title was changed. The journal now focuses on the following topics: Systems theory, Systems engineering, Systems control, Systems modeling and statistics, Systems analysis, Optimization and management, Intelligent systems, emphasizing complex systems, Related problems of complexity, Methodology, Practical applications in a wide variety of disciplines. The journal emanates from the Institute of Systems Science, Chinese Academy of Sciences, and is edited by GUO Lei, the Institute's Director. Prof. Guo and his predecessor, CHEN Hanfu, who is a member of the Editorial Advisory Board, are well known in the international systems science and control communities and publish articles of the highest quality on theories, methodologies and applications of systems science and complexity science.