Local derbies are, and always have been, the lifeblood of professional football. They are the games that encapsulate everything that football means to the community in which they are based
Families and workplaces are divided by allegiance to their respective sides, and close friendships are put on hold for 90 minutes as two opposing footballing factions do battle on the pitch.
At times, deeper community divides come into play and divisions may spill over into conflict both on and off the pitch.
So, ahead of the coming meeting between Manchester clubs United and City, let's take a look at 10 of the best local rivalries in football.
The long-standing rivalry between Manchester United and Manchester City has taken on a new dimension in recent years, with "noisy neighbours" City becoming a major force in the English game.
With the two sides currently the top two sides in England by some distance, the game has regularly been influential in deciding the destination of major titles in recent years.
Both United and City have emerged victorious from memorable encounters in both league and cup. The next step, surely, is a high-profile European encounter.
The game may not always have registered among the top derbies in football, but its recent importance means it is now one of the most hyped games anywhere in the world.
Vasco da Gama vs. Flamengo has long been Rio de Janeiro's most traditional derby, for example, but the Fla-Flu derby involving Fluminense has become the most famous on an international level.
Of all the Italian derbies, it is the Derby della Capitale between Roma and Lazio that manages to capture the attention of supporters like no other.
At last November's meeting between the two sides, a Molotov cocktail was reportedly thrown at police, a supporter was stabbed in the build up and Lazio were even unable to fly their eagle mascot due to the tension between the two sides (via The Guardian).
With AS Roma formed by the merger of three of the capital's sides, Lazio pride themselves on being the team that resisted Mussolini's plans to form a capital-based superteam to rival the power of Inter, AC Milan and Juventus.
The divisions between the teams still run clear and, with Lazio's ultras famed for their right-wing links, tension between the two sides has sometimes taken on a racist tone in recent years. On the pitch, also, the game is never far away from controversy.
With two sets of passionate supporters hailing from steel-working communities in cities just 15 miles apart in the Ruhr industrial region of Germany, it is easy to see just where the passion arises from.
Emotions reached their peak in recent years in 2006-07 when Dortmund beat their rivals to deny Schalke what would have been a major step towards a first league title in 49 years.
Dortmund enjoyed dominance in the early years of the fixture but have seen Schalke claw themselves back to equal footing in the head-to-head standings between the teams.
Supporters of Schalke, though, are currently forced to watch their rivals performing well in the Champions League, having also won two consecutive Bundesliga titles in 2011 and 2012.
The Eternal Derby between Belgrade-based sides Red Star and Partizan is another derby with a history highly linked with politics, with both sides formed by differing political groups under communist rule.
Only once in the past decade has either side finished outside the top two places in the Serbian league, meaning that it is yet another tie with a very real influence on the distribution of honours and, thus, the rivalry remains as strong as ever.
In fact, since the break up of Yugoslavia removed Croatian sides Hajduk Split and Dinamo Zagreb from the equation, the derby has gained importance as a direct result of the two sides' dominance of the domestic league.
It is a rivalry that extends well beyond footballing boundaries, with the clubs' basketball and handball sides also fiercely competitive at the top of their disciplines.
Penarol and Nacional are just two of a huge number of Uruguayan sides hailing from the city of Montevideo, but are without doubt the two biggest and most successful.
The argument rages between the two sides over which is the oldest of the two clubs, with the exact date of Penarol's founding disputed. The passion, though, rages on over 100 years later.
With Penarol currently leading Nacional for both Libertadores titles and domestic championships, it is they who claim superiority. In recent years, though, Nacional have closed the gap considerably on their rivals.
There remains, though, a fierce divide between the two sides. Penarol are the team of the people, with a hugely passionate working class fanbase who are fiercely loyal to their yellow and black flag.
On the other side lie Nacional, the team of the middle classes. Just as passionate, their supporters may lack the colour and noise of their rivals, but there is no doubting their commitment to the cause on matchdays.
Scotland's Old Firm derby is renowned worldwide for the passion shown by both sets of players, supporters and, as shown, coaching staff on a regular basis.
The two sides have won nearly 100 league titles between them and have been the two dominant forces of Scottish football for the majority of the history of the game in the country.
The two most popular sides of the game north of the border, though, are deeply divided on the basis of both religion and politics.
Rangers' supporters are typically associated with protestant beliefs and allegiance to Great Britain, while Celtic have a large catholic supporter base, with many supporters hailing from Irish Republican backgrounds.
The divides lie much deeper than just footballing or postcode rivalry and, thus, have continued to cause flare-ups despite attempts to cool tensions.
The Cairo derby is one of Africa's most anticipated sporting events, with the Egyptian capital's two biggest sides supported by two sets of highly passionate supporters with highly partizan views.
The differences between the two sides extend back to the colonial era, with Al-Ahly seen to be the team of the Egyptian nationalists. Zamalek, conversely, were the team of the outsiders.
As this article on the Guardian website explains, it is a division that still exists. Al-Ahly are the team of the working class, while Zamalek's supporters traditionally hail from more prosperous backgrounds.
So passionate has the rivalry been that violence has been par for the course, with all clashes between the two sides now played in neutral stadiums.
Both sets of supporters, though, recently stood side-by-side to topple the regime of Hosni Mubarak (via CNN), although Al-Ahly's supporters were later targeted in the Port Said stadium disaster that left dozens dead (via BBC).
The tragedy once more saw the two sets of fans united in condemnation, with divisions put aside in pursuit of a greater cause.
The two sides are by a great distance the two best-supported clubs in Argentina and, with the two clubs holding very different socio-economic backgrounds, fixtures between the two sides are passionate affairs.
In this case, it is Boca Juniors who are seen as the team of the people having stuck to their roots in the less affluent area of La Boca.
River Plate, on the other hand, became known as "Los Millonarios" due to their supposedly upper-class supporter base, having moved from La Boca to the wealthier district on Nunez.
The game, though, has sadly been marred with violence between the two sets of fans. The most serious incident occurred in 1968, with 71 Boca Juniors fans killed in a crush at their rivals' El Monumental stadium.
The exact cause of the disaster has never been officially decided upon, with stories placing blame upon both sets of supporters for causing the stampede, with tragic consequences.
The Intercontinental derby between Fenerbahce and Galatasaray sees Turkey's two biggest clubs come head-to-head in a clash that bridges the city of Istanbul.
While Fenerbahce's traditionally working class supporter base hails from the Asian side of the Bosphorus strait, Galatasaray are generally seen as a club of the middle classes based on the European side of the city.
It is a rivalry that has grown in ferocity ever since the first trouble between supporters in a match in the 1930s.
The most famous incident in the recent history of the clash came in 1996, when the two clubs met in a Turkish Cup final that would live long in the memory.
Fenerbahce were expected to comfortably dismiss their rivals and were seen to be arrogant in the build up to the fixture.
Thanks to goals from Welsh striker Dean Saunders, though, Galatasaray downed their rivals over two legs, prompting manager Graeme Souness to plant the club's flag in the centre circle at Fener's Sukru Saracoglu Stadium.
The incident predictably provoked a passionate response from the home support, and Souness remains a hated figure at the club to the present day.