In its largest enlargement, the EU admits ten countries, mostly from Central and Eastern Europe, including Poland, the Czech Republic and the Baltic states.
Euro cash enters circulation in twelve European Union countries, replacing national currencies such as the franc, the Deutsche Mark and the lira.
A brief war between Russia and Georgia over South Ossetia and Abkhazia; Russia afterwards recognises both regions as independent states.
The British and Irish governments and Northern Ireland's parties sign a peace agreement, ending most of the violence of the Troubles.
Dolly the sheep, the first mammal cloned from an adult somatic cell, is born at the Roslin Institute in Scotland.
CERN announces that the ATLAS and CMS experiments at the Large Hadron Collider have observed a particle consistent with the Higgs boson.
After capturing Srebrenica, Bosnian Serb forces kill more than 8,000 Bosniak men and boys; international courts have ruled it a genocide.