This document provides an overview of the modern nation-state system. It discusses the origins of nation-states in the Peace of Westphalia in 1648. It then outlines the essential elements of nation-states as territorial integrity, sovereignty, nationalism, and equality. The document notes that nation-states are now facing challenges from trends like globalization, decentralization, sub-nationalism, and regional groupings. In conclusion, it discusses potential long-term replacements for the nation-state system like continent-sized governance units under a world government framework.