The world awoke Friday morning to the shocking news that a majority of U.K. citizens had voted to leave the European Union and Prime Minister David Cameron would be leaving office in three months, making way for a new leader who supported the Leave campaign.
In the EU referendum known as "Brexit," a majority of U.K. citizens, 52 to 48 percent, voted to sever ties with the EU by 2019.
So what makes this referendum so significant? Below are five things about the U.K.'s long relationship with the EU
1. Britain's EU Founding Father
Winston Churchill, the famed British prime minister, is considered one of the "Founding Fathers" of the EU.
Churchill was a supporter of creating a "United States of Europe" in which the various states of the continent would ally and never wage war on one another again.
"We must build a kind of United States of Europe. In this way only will hundreds of millions of toilers be able to regain the simple joys and hopes which make life worth living," argued Churchill in 1946.
"There is no reason why a regional organization of Europe should in any way conflict with the world organization of the United Nations. On the contrary, I believe that the larger synthesis will only survive if it is founded upon coherent natural groupings."
While what is now called the EU was not created until 1993, the international organization traces their lineage to the efforts of Churchill and many of his peers to create a so-called United Europe.
2. Initial Distance
Despite the support from Churchill, the U.K. hesitated to take an active role in the earlier incarnations of the EU.
"But as the European Coal and Steel Community was forged in 1951, Britain stood on the sidelines; and it declined an invitation to join the six founding nations of the European Economic Community in signing the Treaty of Rome in 1957," noted the BBC.
"One of the architects of the ECSC, Frenchman Jean Monnet, said: 'I never understood why the British did not join. I came to the conclusion that it must have been because it was the price of victory — the illusion that you could maintain what you had, without change.'"
3. Initial Rejection
Ironically, there was a time when the U.K. wanted to be part of a grand alliance of European powers but had its request for membership rejected.
During the 1960s, the U.K. twice attempted to get membership with the European Economic Community, an earlier incarnation of the EU.
French President and World War II hero Charles de Gaulle was responsible for both vetoes, arguing in 1967 after again rejecting the U.K.'s request that the British Isles held "hostility" for the mainland.
"[De Gaulle] said London showed a 'lack of interest' in the Common Market and would require a 'radical transformation' before joining the EEC," recounted the BBC.
"He went on to list a number of aspects of Britain's economy, from working practices to agriculture, which he said made Britain incompatible with Europe."
4. Finally a Member
Things changed in the 1970s. With de Gaulle dead, the French president was no longer present to veto the U.K.'s attempt to enter the multinational organization.
Under Tory Prime Minister Edward Heath, the British joined the EEC at the beginning of 1973 alongside Denmark and the Republic of Ireland.
In 1975, British citizens held a referendum on EEC membership with 66 percent of the nation agreeing to the membership in the continental body.
5. Growing Tensions
The EU referendum was not something that appeared out of a vacuum, but rather came about through a growing resentment over membership with the EU and the staggaring costs to U.K. taxpayers.
"In 2015 the U.K. government paid £13 billion to the EU budget, and EU spending on the U.K. was £4.5 billion. So the U.K.'s 'net contribution' was estimated at about £8.5 billion," according to Full Fact, U.K.'s independent fact checking charity.
The U.K. had originally joined the EEC to help boost their lagging economy. But disillusionment first emerged when the promised economic boom failed.
Over the past several years, many Britons came to realize they had no influence over EU policies and laws that dictated their lives.
UKIP's leader Nigel Farage, who's also a member of the European Parliament, has been the driving force behind the campaign to leave the EU, educating voters on the bureaucracy's stranglehold on U.K. businesses and self-governance.
With pressure mounting from UKIP and euroskeptic members of the Conservative Party, Prime Minister David Cameron was forced to promise that if the Conservative Party won the 2015 election he would guarantee the EU referendum would be voted on before 2017.
Fomer mayor of London Boris Johnson joined the Leave campaign back in February in what some believe was a strategic move to increase his chances of succeeding David Cameron as the next prime minister.
"Imagine having £1,000 more to spend each year. By leaving the EU, each household could be better off by this amount — through cheaper food bills, no membership fees, with the cost of regulations lifted, too," argued Leave.EU, a site supporting Brexit.
"Imagine not having our laws dictated to us by Brussels. Instead, MPs would become accountable to the public and we would once again be able to make and decide on our own laws."