Voting is under way on the final day of elections for the European Parliament, with nationalists mounting a challenge to pro-EU parties.
In total, 400 million people are eligible to take part. Voting has already taken place in seven of the EU's 28 member states.
Results will be released after polls close at 21:00 GMT (22:00 BST) on Sunday.
In Britain the focus will be on how pro- and anti-Brexit parties perform.
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.
Across Europe, right-wing nationalist parties have mounted a co-ordinated challenge to the centre-right and centre-left groupings that have been the dominant power in every European Parliament.
Italy's League party has joined forces with other right-wing groups including Germany's AfD, the Finns Party and the Danish People's Party to create the European Alliance for People and Nations.
In doing so they hope to change the balance of power in the EU.
Although nationalist and Eurosceptic groups are currently among the smallest in the European Parliament, support has grown for anti-immigration parties since the 2014 election.
European elections 2019 - who voted and when?
- 23 May: Netherlands, UK
- 24 May: Ireland, Czech Republic (which also votes on 25 May)
- 25 May: Latvia, Malta, Slovakia
- 26 May: Austria, Belgium, Bulgaria, Croatia, Cyprus, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Italy, Lithuania, Luxembourg, Poland, Portugal, Romania, Slovenia, Spain, Sweden
In the Netherlands - one of the first countries to vote on Thursday - the centre-left Labour party has already been celebrating what it believes is a political comeback based on exit polls it has seen.
The exit polls are not necessarily an accurate indication of the result.
The party had plummeted in the 2017 national elections from 38 seats in parliament to nine, apparently as punishment for its role in the coalition government where it helped pass austerity measures.
The vote in the UK, meanwhile, was never meant to happen following its decision to leave the European Union in a 2016 referendum.
But wrangling over an exit deal with the EU has delayed Brexit and meant that Britons were called to the polls on Thursday.
Brexit has been a key issue for voters and veteran eurosceptic campaigner Nigel Farage set up the Brexit Party, demanding an immediate withdrawal from the EU.
The two main parties, Labour and Conservative, fear a backlash over their handling of Brexit.
Other, pro-EU, parties however are hoping to see a surge in the polls from "remain" supporters.