On 3 October 1990 the process of reunification of Germany was concluded and as a result the German Democratic Republic (GDR/East Germany) joined the Federal Republic of Germany (FRG/West Germany) and Berlin was reunited into a single city.
Andrzej Włusek: 3 October 1990 - Reunification of Germany
The Fall of the Berlin Wall, 1989. Wikimedia / CC BY-SA 3.0
German Unity Day

The Fall of the Berlin Wall, 1989. Wikimedia / CC BY-SA 3.0