The 'complex environment' is a label to describe an operations context that different constituencies give different names. Business might call these environments 'emerging' or 'frontier' markets; multilateral donors or governments might call the same places 'fragile states' or 'least developed' or 'developing countries'. The 'complex environment' is a useful analytic category because it unites a diverse set of actors on the same question: How do we make sense of the environment in which we operate? 1 By drawing on the research in economics, political economy and the social sciences, this Paper describes the political and economic dynamics that are shaping complex environments and that are relevant for investment in countries affected by, or emerging from, violent conflict.