Arrange the following events related to the European Union (EU) in chronology:
1. Introduction of Euro Currency
2. Establishment of EEC
3. Signing of Maastricht Treaty
4. Britain's Exit (Brexit) Referendum
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To remember the sequence of the EU, think of it as a progression: first came the Economy (EEC), then the Political Union (Maastricht), then the Money (Euro), and finally the modern challenges (Brexit).