Computer simulation is a fundamental discipline for studying complex systems. Like any other discipline, simulation must grow and be fine-tuned so that it maintains its position as the base methodology for doing computational science and constructing digital worlds. We discuss ten areas outside of simulation and demonstrate growth by identifying relationships between simulation and each of the areas. We outline each field by describing it briefly and then specifying outstanding issues which remain to be resolved. We have found that we are better able to characterize basic simulation methodology by integrating and extending simulation within the context of other fields.