The Lisbon Treaty has formally come into force after eight years of controversy and debate over the future shape of the European Union.
The Treaty increases powers for the European Commission, European Parliament and the European Court of Justice, including in the area of justice and home affairs.
The right of national veto in EU decision making is removed in dozens of areas, although unanimity will still be required to pass EU laws on tax, foreign policy, defence and social security.
National parliaments also get increased powers of scrutiny over EU lawmaking.
Most attention is on two new top jobs, the most immediate and visible effects of the treaty which came into being at midnight - the EU's first president Herman Van Rompuy and new foreign affairs chief Catherine Ashton took office today.
The 27 EU heads of state and government chose Mr Van Rompuy for the top job at a summit last month.
His post, the President of the European Council, is for a two-and-a-half year term renewable once, giving the bloc both a human face and a more stable presidency than the current system of rotating the EU summit chair between nations on a six-monthly basis.
The rotating presidency remains and will chair discussions at individual policy level, with Spain taking over the role on 1 January, 2010.
'Today EU citizens are heading into a new era,' said Swedish Prime Minister Fredrik Reinfeldt, whose nation retains the old-style rotating European Union presidency until the end of the year.
'Today is the first day for a more efficient, more modern and more democratic EU, for all citizens,' he added in a statement.
The treaty, drawn up to replace the aborted EU constitution, is designed to boost the bloc's global standing and streamline the institutions which represent half a billion people in 27 countries.
'The Treaty of Lisbon puts citizens at the centre of the European project,' European Commission President Jose Manuel Barroso said in a statement.
Now 'we can focus all our energy on delivering what matters to our citizens,' he added, in reference to the years of institutional navel-gazing which ended with the treaty coming into effect.
