In December 1991, the Soviet Union dissolved into fifteen independent republics, of which the Russian Federation was the largest. On January 1, 1993, Czechoslovakia split into two separate countries, the Czech Republic and Slovakia, in a “Velvet Divorce” [PDF].
The breakup of Yugoslavia in 1991 wrought a decade of war that devolved into ethnic cleansing and genocide. Eventually, Bosnia and Herzegovina, Croatia, Kosovo, North Macedonia, Montenegro, Serbia, and Slovenia would all become independent states.
The fall of the Berlin Wall and the collapse of the Soviet Union accelerated the push for deeper European integration, a project which had begun in earnest in the wake of World War II, with the founding of the European Coal and Steel Community in 1951 and the European Economic Community in 1958.
The European Union (EU) was formally established by the 1992 Maastricht Treaty.
Maastricht established a framework for a common currency and a common defense and security policy; the 2007 Lisbon Treaty created the EU’s current structure.
Source: After The Berlin Wall