Are the Lib Dems facing wipeout? Can Labour hold on in its traditional strongholds? And will May secure the kind of majority that will fortify her leadership of the Tories?
We've picked 10 key seats – five in the capital, and five across the country – to help figure out the answers to some of these questions in the early hours of Friday.
First up - London
Ealing Central and Acton - Expected Result 02.00 – 03.00
Labour's Rupa Huq is trying to hold on, and if she does so it may be because of support from rival parties. Backed by Gina Miller's Best For Britain campaign as an anti-Hard Brexit politician, Huq has also been boosted by the decision by the local Green party not to field a candidate against her.
In 2015, the Greens picked up less than 2,000 votes, but the Ealing seat is an ultra-marginal with Huq elected on a majority of just 274 last time out, making this a key test for progressive alliances.
The seat is on the Tory target list and one that could give an early indication of how Theresa May's party is performing.
Bermondsey and Old Southwark - Expected Result 03.00 – 04.00
A battle of personalities in South London where Lib Dem Simon Hughes is hoping to unseat Labour's Neil Coyle.
Labour are confident their ground game in the seat is stronger than the Lib Dems', and Coyle has said his status as a rebel in Jeremy Corbyn's party stands him in good-stead with the locals.
But Hughes was MP for the constituency for more than 20 years. A defeat for him in Bermondsey might give some indication of the public appeal of the Lib Dems' old guard.
Vauxhall - Expected Result 03.00 – 04.00
With a strong majority of 12,708 in 2015, Labour Brexiteer Kate Hoey should be safe in Vauxhall against a first-time campaigner for the Lib Dems. Unless...
The area was strongly pro-Remain in the Brexit referendum, and Tim Farron's party haven't been shy about reminding people of Hoey's participation in a Thames Brexit flotilla alongside Nigel Farage last Summer.
A diversity of nationalities, incomes and social backgrounds make Vauxhall difficult to use as an indicator of broader results, but Hoey may represent the most significant scalp the Lib Dems can secure.
Brentford & Isleworth - Expected Result 04.00 – 05.00
Another ultra-marginal, with Labour's Ruth Cadbury securing victory in 2015 by just 465 votes. Cadbury defeated then-MP Mary Macleod, who is back for a second bite at the cherry this time around.
A key marginal, the seat had long followed the direction of the country up until Cadbury's victory in 2010.
It is the kind of seat that will point to a good result for May and a strong majority in the final result.
Richmond Park and North Kingston - Expected Result 04.00 – 05.00
It was Zac Goldsmith's defeat in a by-election late last year that first suggested a rumoured Lib Dem revival could lead to some concrete results.
The victory helped solidify the broader Lib Dem strategy pursued throughout this campaign, with a pro-Single Market candidate vowing to represent the interests of Remain voters.
Both sides have brought the big guns down to the side of the Thames – Menzies Campbell has been spotted in the leafy constituency backing Lib Dem Sarah Olney, while chancellor Philip Hammond was in town to back Goldsmith earlier today – indicating that neither side yet feel confident.
A late result is expected, but a win here would illustrate the Tories' ability to recover support from the nation's Europhiles in future, even with Brexiteer candidates.