Both goals are necessarily speculative. The study of complex systems, whether natural or social, is still in its infancy. While many insights and plausible conjectures have been generated, the long term importance of this work is still unclear. For our purposes, a system is said to be complex when it exhibits some type of order as a result of the interactions of many heterogeneous objects. Economists have begun to use complex systems as the basis for formal modeling precisely in order to understand certain aggregate features of environments which are characterized by many heterogeneous actors.
Examples are easy to construct.
A stock market is comprised of many traders with idiosyncratic beliefs about the future. The actors exchange information and react to some types of common information, but stock prices are ultimately determined by a large number of decentralized buy and sell decisions. In a very different area, the composition of residential communities is determined by the individual preferences and location decisions of individual families. Notice that in each case, there is a feedback between the aggregate characteristics of the economic environment under analysis and the individual actors which comprise that environment. Movements in stock prices influence the beliefs of individual traders and in turn influence their subsequent decisions.