Complex systems is a practial field because the systems that we are interested in designing, building, repairing or influencing are complex. Applications of these concepts exist in
Medicine, Engineering, Business, Economics, Management, Government, Education
Thus, both the general approach to understanding, and the tools for modeling, simulating or describing complex systems have a wide variety of direct applications. The development of applications is inherent in the effort to unify the study of systems, whether they are natural or artificial, physical, biological or social/economic.