Call it the Greta Thunberg effect – or just concern about the environment – but the experts have been looking out for changes in the Green vote across Europe.

In Germany, this Green MEP is very excited about the exit polls she's seen:

And look how happy the Greens in France are – the leader of the Green EELV party has tweeted this video of some very happy supporters:

Image source, EPA

Greece's conservative opposition leader, Kyriakos Mitsotakis, is celebrating - insisting he has beaten Prime Minister Alexis Tsipras in the European Parliament vote.

You may remember that left-wing leader Alexis Tsipras has been in power since the bailout crisis came to a head in 2015.

"It is obvious that the Greek people have withdrawn their confidence in this government," says Mr Mitsotakis, leader of New Democracy.

Greeks are set to vote later this year, and for Mr Mitsotakis that can't come soon enough.

"The prime minister must assume his responsibilities. He must resign and the country should hold national elections as soon as possible."

Belgians have not just been voting in European elections. They've had a federal election and a regional vote too. That's a lot for the vote-counters to get right. All eyes in the federal vote are on Flemish far-right party Vlaams Belang.

French President Emmanuel Macron's party was always going to be a good fit for Europe's Liberals and Democrats group ALDE. But they had their differences and the marriage has only just been confirmed.

As we said, it's been higher than average in most EU member states. In Germany, particularly so.

Image source, EPA

Turnout estimates for 27 countries - every member state except the UK - suggest that more people have turned up to vote than in any European election in the past two decades.

A European Parliament spokesman said turnout was estimated to be 51%.

The UK estimate is due later, and once included the overall turnout is expected to be 49-52%, he said.

For comparison, the last time European-wide turnout was over 50% was in 1994., external

A reminder that the BBC is following UK law on reporting any exit polls or projections that might exist out there.

Under UK law, there are restrictions about what broadcasters can say while polls are open.

The European Parliament's own website is providing up-to-date exit polls, external from EU member states as well as projecting what they mean for the make-up of the Parliament.

You can read more about the restrictions here.

Image source, Reuters

One development to watch out for is the possible emergence of a new right-wing, nationalist group - the European Alliance for People and Nations.

Led by Italy's right-wing nationalist leader Matteo Salvini, it was announced with the support of just four parties.

But last weekend 12 parties gathered for a landmark rally, including Marine Le Pen.

Many commentators expect the group to do well and increase the far-right's power in the European Parliament. However, things aren't looking quite so good for one of the leaders, Dutch anti-Islam politician Geert Wilders. One of his own Freedom Party senators, Dannij van der Sluijs, said on Friday after seeing exit polls, that Mr Wilders should step down. "I think his time is past," he said.

Marine Le Pen's National Rally (RN) are jubilant.

They think they've beaten President Emmanuel Macron's ruling centrist LREM party. RN spokesman Sébastien Chenu says Emmanuel Macron "gets a slap tonight from the French".

And Mrs Le Pen wants him to dissolve parliament.

Greece's left-wing Syriza government is facing elections this autumn, so tonight's result is being keenly watched as a precursor to what might happen.

Conservative New Democracy supporters have been celebrating what they think is a win.

They'll have to wait - and judging from what this Capital.gr reporter says - the Syriza finance minister thinks they're premature.

Queues like the one below in Brussels were repeated outside embassies around Europe, as Romanians voted not just in the European Parliament poll, but also on a referendum about controversial justice reforms.

One of the reforms is approving amnesties for offences linked to corruption. The Social Democrat government urged voters to boycott the poll, which was called by President Klaus Iohannis.

Polls closed at 19:00 BST (20:00 CET).

Ireland is one of the few countries to use the single transferable vote method - widely thought of as being a very fair method, but incredibly complicated to count as each ballot paper is "transferred" from candidate to candidate.

Journalist Nicky Ryan from Ireland's TheJournal.ie tweets from the Dublin count centre where stacks of ballots are being hauled about - while some staff take a well-earned rest. And there's been a local election on in Ireland too.

Read more about the different voting systems here.

In the run-up to the vote, there was a lot of speculation that the Greens might do well in Germany.They certainly think they have - tweeting "Thank you for this awesome result!"

The People's Party has had a rough week, having lost their far-right coalition partner in the aftermath of a video scandal. And Monday is set to get even rougher when Chancellor Sebastian Kurz faces a no-confidence vote.

But they're celebrating tonight based on exit polls they've seen.

Image source, Reuters

A reminder that these elections will also have an impact on who will become the next European Commission president.

Throughout the past few weeks, candidates from the main parties, known as Spitzenkandidaten, have been campaigning across Europe.

Our Brussels reporter Adam Fleming explains the process below - but there's also a chance that the national leaders might abandon this process and choose an outside favourite instead.

Dutch voters were, along with the UK, first to go the polls on Thursday and the Dutch Labour party have already been celebrating what they think will be a good night for them. But for the official results, the waiting goes on.

Image source, Reuters

Initial results and projections will be announced from the European Parliament in Brussels, where MEPs hoping to keep their jobs and the press alike can watch the contest unfold on the big screen.

So what happens next? Follow these links to find out how it all works and what to look out for:

• How voting works across Europe, despite different national rules
• A look at whether this election could be a moment of truth for nationalists
• Some interesting big-picture things to watch out for in the results
• The controversy in the UK when some EU citizens were turned away from polling stations

Voting began on Thursday in the UK and the Netherlands, then continued across the EU.

But voting is still ongoing in several European countries where polling day is Sunday.

UK election law prevents the BBC, along with other UK broadcasters, from reporting details of campaigning or predictions of results until all polls have closed.

We’ll still bring you reaction from around Europe – from those parties that think they have done well and those who don’t – until the official results are released.

You can read more about the BBC’s election coverage rules here.

Welcome to the BBC’s live online coverage of the European Parliament elections across all 28 countries.

We’ll be bringing you the latest news as results are released late on Sunday – both the national battles and what it means for the pan-Europe power blocs.

In the UK there will also be a particular focus on how the mainstream parties have fared in light of the continuing Brexit crisis and the announcement by Prime Minister Theresa May to resign next month.