Huge body blow for the EU
The Leave vote in the UK is a huge body blow for the EU - already reeling from the migrant crisis, the euro crisis and fears about what is seen as an aggressive Russia next door.
Brexit could prove to be the biggest blow yet. It sends shockwaves far beyond British borders.
The UK gave the EU a second seat at the UN Security Council, one of only two serious military forces (alongside France), respected diplomatic expertise and a driving force behind making the single market more competitive.
All that will now disappear from the EU display cabinet.
And as Britons anxiously scan the markets, watching the effect of Brexit on the pound, Europeans fear for the future of what had been a nervously recovering euro.
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Deeper crisis for Greece perhaps? Italy too is a huge concern.
How will this impact the pockets of hundreds of thousands of families across the continent?
The EU also worries Brexit could reverse 70 years of European integration.
In all my years watching European politics, I have never seen such a widespread sense of Euroscepticism.
Plenty of Europeans looked on with envy yesterday as Britain cast its in-out vote.
Many of the complaints about the EU raised by the Leave campaign resonated with voters across the continent.
Across Europe leading Eurosceptic politicians queued up on Friday morning to crow about the UK referendum result.
"Victory for freedom," tweeted Marine Le Pen of France's National Front.
She has called for a vote on EU membership in France. There are similar voices in Italy, the Netherlands and beyond.
The mood in Brussels this morning is deeply gloomy.
The Brexit vote sends screaming alarm bells; warning that the EU in its current form isn't working.
Two processes will soon be launched here - both fraught with difficulty.
Untangling the UK from everything EU and negotiating a new relationship once David Cameron or his successor formally starts the Leave process.
And a political scramble as the EU tries to save itself, possibly disintegrating further in the process.
Expect deep divisions between EU nations and Brussels bureaucrats about the direction the EU now takes.
Closer union to show a united European front, or reform and a rethink of the European project?
Prime ministers across Europe look nervously over their shoulders at increasingly influential Eurosceptic, more nationalist-minded political rivals.