1. The clubs
Real Madrid were founded in March 1902 by Julián Palacios and the brothers Juan and Carlos Padrós, under the initial name Madrid Foot Ball Club. Throughout their history, Los Blancos have remained an organisation that belongs to its members (who, according to the latest official figures, now number 92,830), rather than a single owner. When Spanish football teams were forced to become public limited sports companies ('sociedades anónimas deportivas') in 1992, Real were, alongside Barcelona, Osasuna and Athletic Bilbao, one of four clubs permitted to retain their fan-owned status.
Created in 1970 by a merger between Paris FC and Stade Saint-Germain, Paris Saint-Germain do have a single owner: the Qatar Investment Authority, a fund controlled by sheikh Hamad bin Jassem bin Jabr Al Thani, a member of the Qatari royal family. QIA acquired the club outright in 2012 and, since then, has built a side whose objective is to conquer Europe. PSG's president is Nasser Al-Khelaifi, a Qatari former tennis player and a close associate of the sheikh's, who is also CEO of the broadcaster beIN Sports.
2. The squads
The Real Madrid and PSG squads are among the most valuable in the world: according to stats specialists Transfermarkt.com, Real's is worth 858.5m euros, second only to Barcelona, while the Ligue 1 leaders are fourth on the list with 756.5 million. Both clubs are also major presences on the website's ranking of individual players' market values: indeed, Los Merengues have four of the top 25 - Cristiano Ronaldo: 120m; Toni Kroos: 80m; Isco: 75m; and Gareth Bale: 75m. PSG have two, both of whom make it onto the podium: Neymar's estimated value of 180m sees him lead the way, and Kylian Mbappé is third on 120m.
3. The stadiums
A comparison of Real Madrid and Paris Saint-Germain's stadiums leaves little room for doubt as to which of the two is a team with more than a century under its belt as a European powerhouse, and which - though clearly now a major force - is a more recent creation with much of its history still to be written.
Initially called Nuevo Chamartín before being renamed in honour of Real Madrid's legendary former president, the Santiago Bernabéu has been the LaLiga giants' home since 1947, seats 81,000 and is on Uefa's 'Elite Stadiums' list. The ground is set for a significant facelift that will see the addition of a retractable roof, although the plans have not been without controversy, given that they are expected to cost 400m euros and lower the Bernabéu's capacity by 2,000.
Meanwhile, PSG's stadium, the Parc des Princes, was officially opened in 1972 and has hosted the club's home fixtures since 1973. Between 2014 and 2016, the arena underwent redevelopment to bring it up to the standards of a top-level European club. However, its capacity is well short of the Bernabéu's: just 48,500.
4. Social media
When it comes to social-media presence, Real Madrid come comprehensively out on top: between Twitter and Facebook, the Spaniards boast 153m followers, while PSG trail on 40.5m. Cristiano is the most followed of the clubs' players, with 122m on Facebook and 69m on Twitter, with Neymar the next-most popular with 38m and 60m, respectively.
5. Past meetings
Real Madrid and Paris Saint-Germain have met six times, with an even-stevens record of two wins and two defeats each, in addition to two draws. On the two occasions that the sides have faced off in European knockout ties, however, it has been the Frenchmen who have been victorious: in both the 1992/93 Uefa Cup and the 1993/94 Cup Winners' Cup, a 'Quinta del Buitre' on its last legs was seen off by the PSG of George Weah and David Ginola. Most recently, in the 2015/16 Champions League group stage, the teams played out a goalless stalemate in Paris before Nacho Fernández's goal clinched a 1-0 win for Real at the Bernabéu.
6. The trophy cabinets
Nowhere is the gulf in history more apparent than in Real Madrid and PSG's silverware hauls. Real have a total of 93 domestic and international trophies, including 12 European Cups, 33 LaLiga titles, 19 Copas del Rey, three Intercontinental Cups, three Club World Cups... Meanwhile, Paris's collection of honours is significantly less impressive, with just the two continental trophies: a Cup Winners' Cup and an Intertoto Cup. Add in six French championships and 11 Coupes de France, and PSG's is a trophy cabinet that pales in comparison to its brimming Bernabéu counterpart, although it is now increasing in size at a rate of knots.
7. The form guide
There can be no debate about which team comes into the tie in better nick: PSG arrive in Madrid for Wednesday's first leg with Ligue 1 all but sown up, having also secured qualification for the Coupe de France quarter-finals and Coupe de la Ligue final. In their domestic league, Unai Emery's men are averaging more than three goals a game, while they hit a record total of 25 in the Champions League group stage - 4.16 per match - and conceded just four. Their terrifying attacking trio of Neymar, Mbappé and Edinson Cavani have plundered 70 goals between them in 2017/18 (27, 15 and 28, respectively).
Real Madrid, on the other hand, were dumped out of the Copa del Rey by Leganés and have endured a wretched LaLiga title defence: Zinedine Zidane's side sit fourth in Primera División, a whopping 17 points behind leaders Barça (albeit with a game in hand). They have lifted three trophies already this season, but none can be considered a major title and all really belong to their fantastic 2016/17 campaign: the Uefa Super Cup, the Spanish Super Cup and the Fifa Club World Cup. The Champions League is all that can save their season.