CERN restarts the Large Hadron Collider, which has been shut down since a serious failure in Sepember 2008

The Treaty of Lisbon is passed into law in the European Union

A major earthquake around L'Aquila, in Italy, kills more than 300 people after experts advise local people that it is safe to stay at home

A plane carrying the president of Poland, Lech Kaczynski, and other high Polish officials crashes on the way to a commemoration of the Katyn massacre, killing all 96 people on board

Volcanic ash from Eyjafjallajökull, a volcano beneath a glacier in Iceland,disrupts northern Europe air traffic for several days

Greece is promised an EU and IMF bail-out package of 45 billion euros to cope with its high level of national debt

Greece's credit rating is downgraded by Standard & Poor to BB+ ('junk'), causing a run on global stock markets

Severe austerity measures in Greece persuade Germany to back an increased EU and IMF bail-out package of 110 billion euros

The UK general election results in no overall majority, with the Conservatives winning 306 seats, the Labour party 258 and the Libereral Democrats 57

Conservative leader David Cameron becomes UK prime minister, forming a coalition government with the Liberal Democrats and appointing Nick Clegg as his deputy prime minister

The Solar Impulse, promoted by Bertrand Piccard and piloted by André Borschberg, becomes the first solar-powered aircraft to fly for more than 24 hours

CERN announces its successful production and brief capture of atoms of antihydrogen, the first observed example of antimatter

The European Union agrees a rescue package of €85 billion to deal with the financial crisis in the republic of Ireland

Prince William marries Kate Middleton in London's Westminster Abbey in a ceremony watched by millions of viewers around the world

Ratko Mladic, the Bosnian Serb commander wanted for war crimes at Srebrenica in 1995, is arrested in Serbia and subsequently extradited to the Hague

Surgeons in Sweden achieve the first artificial living organ transplant, after using the patient's own stem cells to coat a plastic replica of his windpipe

Goran Hadzic is arrested in Serbia, completing the detention of all 161 people from the former Yugoslavia indicted by the International Criminal Court

Anders Behring Breivik shoots and kills 69 young people on the Norwegian island of Uteya after killing eight with a bomb in government buildings in Oslo

Eurozone leaders agree a second bail-out package for Greece of €109 billion

The funding crisis in the Eurozone extends to fears of potential government default in the large economies of Spain and Italy

In response to Portugal's increasing financial crisis the European Union grants the country an emergency loan or bailout of 78 billion euros

The Shard, an 87-storey building in London designed by Renzo Piano, is completed, becojming the tallest building in the European Union

The Italian cruise ship Costa Concordia crashes into a rock near the Italian island of Giglio, killing 32 people

The European Union imposes an oil embargo on Iran to deter efforts to achieve a nuclear weapon

Russia and China use their Security Council veto to block a UN resolution to end the violence in Syria