This award will fund travel and local expenses for 25 invited participants for a workshop on ?Complex Systems,? to be held at the National Science Foundation in Arlington, VA, September 23-24, 2008. The workshop is being sponsored by the NSF Directorates for Mathematical and Physical Sciences (MPS) and Engineering (ENG). The workshop will assess opportunities for research on complex systems in mathematics, the physical sciences, and engineering. Its primary emphasis will be on cross-cutting principles that will establish conceptual approaches applicable to diverse problems. The workshop deliberations and conclusions will be summarized in a report to the NSF; the anticipated delivery date is October 31, 2008.