The study of complex systems can be viewed generally as an effort to understand the relationships between properties of systems when viewed on different scales. Viewing a system on different scales involves distinguishing details of behavior and understanding how the details give rise to collective behaviors that can be seen on a larger scale even through most of the details are no longer distinguishable. In this talk/paper I provide a brief review of various forms of interactions/relationships between parts of a system that illustrate how collective behaviors can arise. Finally, 1 discuss the complexity profile which is designed to capture the essential idea of considering a system on multiple scales.
