Here's all you need to know about the Trident renewal debate
So, Theresa May will tell MPs not to gamble with the safety of British families ahead of a Commons vote on whether to renew the Trident nuclear deterrent.
But if you're feeling a little confused about the whole Trident debate, we're here to tell you everything you need to know ahead of the vote.
Erm, sorry, but what exactly is Trident?
It's a complete system of submarine-based nuclear missiles and is based on four Vanguard-class submarines. One of them has been constantly on patrol since the system came online in 1994.
The Royal Navy operates the system at Clyde Naval Base on the west coast of Scotland.
So, what's going on tonight?
MPs are set to vote on the renewal of Trident - which will cost around £40 billion. FYI, May will tell them it would be "grossly irresponsible" not to back Trident.
The motion which MPs will vote on states that "the UK's independent minimum credible nuclear deterrent, based on a continuous at sea deterrence posture, will remain essential to our security today as it has for over 60 years, and for as long as the global security situation demands, to deter the most extreme threats to our national security and way of life and that of our allies; and supports the decision to take the necessary steps required to maintain the current posture by replacing the current Vanguard class submarines with four successor submarines".
When May opens the Commons debate, she is expected to say "the nuclear threat has not gone away, if anything it has increased".
How are MPs set to vote?
May will accuse anti-nuclear Jeremy Corbyn of "misplaced idealism" - his Labour Party looks set to split on the issue. The shadow cabinet is calling for MPs to abstain but senior figures such as deputy leader Tom Watson and leadership candidate Owen Smith are backing renewal.
Watson acknowledged the vote was "partisan political game-playing" but described abstaining as an "abdication of responsibility" as Labour splits came to the fore.
Despite the opposition of the SNP and reportedly fewer than half of Labour MPs, the Government will expect to win the vote and proceed with renewing the submarine deterrent.
Labour MP John Woodcock said pro-Corbyn pressure group Momentum may try to intimidate his party colleagues into voting against Trident renewal.
The Barrow and Furness MP told BBC Radio 4´s Westminster Hour: "It's hard to understand why Labour has a free vote on such a fundamental matter of national security except to spare the blushes of the leader, who doesn't believe in the Labour Party's established policies, but let's see."
Trident has been a bit of an election issue in the past hasn't it?
Labour's shadow foreign secretary Emily Thornberry and shadow defence secretary Clive Lewis have insisted the Conservatives are holding the vote simply to "sow further divisions" in Labour because renewal was already agreed in principle in 2007.
The Tories committed in their 2015 general election manifesto to replacing the Vanguard class of submarine which carries Trident missiles with four new successor class boats.
So, how much does Trident cost?
The Government says the latest estimate puts the cost of the four successor submarines at £31 billion over 20 years with a £10 billion contingency - on average 20p in every £100 the state spends.
Oh, and a renewed Trident programme will be operational until the 2060s.
What are some people on Twitter saying about it all?