Status: 3rd in Bundesliga
Nicknames: FC Bayern, FC Hollywood
THE RECORD: Led by the star triumvirate of sweeper Franz Beckenbauer, ace marksman Gerd Muller and keeper Sepp Maier, Bayern were one of the leading European lights of the 1970s, claiming three consecutive Champions' Cups in 1974, 1975 and 1976.
There followed a relatively barren period on the continental front, but in 2001 the Bavarians hit the jackpot again, defeating Valencia on penalties in the 2001 Champions League final in Milan's San Siro. The low point? Undoubtedly their heartbreaking loss to Manchester United in the 1999 final, a game they held in the palm of the hand until conceding two late, late goals.
TACTICIAN: Jupp Heynckes
Bayern could take no more of the stubbornness and confrontational style of Dutch boss Louis van Gaal and, in a bid to calm down the tensions in the dressing room, promptly made arrangements to fill the vacancy with the veteran ex-Real Madrid and Bayer Leverkusen coach Jupp Heynckes.
Authoritative and vastly-experienced, 66-year-old Heynckes is just what the doctor ordered and knows all about the Bayern politics, having taken charge there on two previous occasions (1987-91 and in the run-in to the 2008-09 campaign). He certainly is no stranger to the European football, starring up front for Borussia Monchengladbach when they won the 1975 UEFA Cup and coaching Real Madrid to the Champions League title in 1998.
THE GAMEPLAN: Likely to employ a 4-2-3-1 formation - a legacy from the Van Gaal era - Heynckes' top priority is to give Bayern a much more durable defensive base. Too often last term they were ragged at the back and the new man in charge aims to correct the fault-lines with a far more physical approach, one which sets great store on winning individual duels.
Lone striker Mario Gomez and a trio of attacking midfielders (Franck Ribery, Thomas Muller and Arjen Robben), will be given freedom to express themselves, to improvise and switch positions. In contrast to the patient and methodical build-up play ordered by Van Gaal, the new Bayern should be quicker into their attacking stride, infinitely more direct.
MAIN MAN: Bastian Schweinsteiger
Louis van Gaal's decision to switch the German international from a wide berth to the midfield engine in the centre of the pitch turned out to be a masterstroke.
With his excellent reading of the game, flawless distribution, heads-up support play and work ethic, 'Schweini' is the cornerstone of the Bayern collective.
A one-time schoolboy skier of much potential, he made his Champions League debut back in November 2002 against French side Lens after just two training sessions with the Bayern professionals.
BIG SIGNING: Manuel Neuer
Despite his status as one of the best goalkeepers in the world, his recent €18 million move from Schalke was not greeted with universal enthusiasm by the Bayern faithful. For certain supporter groups at the Allianz Arena, the 25-year-old Schalke academy product is the personification of the 'enemy' due to the apparent lack of respect he showed to Bayern legend Oliver Kahn.
The Champions League brings out the best in him. In 2008 his heroics were the key factor in Schalke's first knockout round victory over FC Porto and last season he defied Manchester United single-handedly in the first leg of the semi-final.
RISING STAR: Thomas Muller
Able to play anywhere in the attacking-third - winger, second striker, in the 'hole' or attacking midfielder - the willowy 22-year-old has covered an enormous amount of ground in the past two seasons, going from Bayern reserve team unknown, to German national team mainstay, to genuine headliner of the world game.
Argentina manager Diego Maradona famously thought Muller to be a 'ball boy' on crossing his path at a press conference after an international friendly in Munich early last year. Six months later the youngster won the World Cup 2010 Golden Boot courtesy of five goals and three assists.
THE X FACTOR: Arjen Robben
As he conclusively proved in the 2009/10 season, a campaign in which his goals did so much to pave Bayern's way to the runners-up spot in the Champions League, the flying Dutch winger is a world-class talent, a scintillating maker and taker of chances.
In his third season at Bayern following his €25 million switch from Real Madrid in the summer of 2009, the 27-year-old has claimed league winners medals with Bayern, Real, Chelsea and PSV Eindhoven, but has yet to strike gold in European club competition. Here's hoping his persistent injury problems do not get in his way this season.
FLAW IN THE MAKE-UP: Coach Heynckes may have difficulty finding the right balance between attack and defence. Bayern have plenty of attacking flair, but flank-gods Ribery and Robben are not known for their defensive graft.
He also needs to bed down his new-look defence quickly, with keeper Neuer, right-back Rafinha and central defender Jerome Boateng all added to his ranks and the experienced Philipp Lahm switching from to the left-side of the team.
WHAT THEY SAY: "You always have to strive for prizes at home and abroad at Bayern and on the back of a disappointing campaign last year, there's every chance they will come storming back in the months ahead," says the club's former striker Jean-Pierre Papin. "The English and Spanish clubs are the favourites, but I fully expect Bayern to be in there punching too."
VERDICT: A quarter-final slot is a realistic target.
Status: 4th in Spanish league
Nicknames: Yellow Submarine
THE RECORD: Champions League semi-finalists in 2006, Villarreal also reached the last four of the UEFA Cup in 2004 and lost out to eventual champions FC Porto in the penultimate round of last season's Europa League.
Their heroics in this competition five years ago could so easily have ended with an appearance in the Paris final, as they came within an ace of beating Arsenal after seeing off Inter Milan in the quarter-finals.
TACTICIAN: Juan Carlos Garrido
Promoted to first-team coach following the sacking of Ernesto Valverde in February of last year, former Villarreal B boss Garrido has excelled in the top job and deserves his crack at the Champions League giants.
Like modern managerial ground breakers Jose Mourinho and Andre Villa-Boas, Garrido hails from a breed of touchline operators who have not taken a traditional route to the top of the game, as he started his coaching career at the age of 23 after failing to make the grade as a player. Still only 42, his success in guiding Villarreal into the Champions League earned him plaudits from all quarters.
THE GAMEPLAN: While Garrido's tactical formation can best be described as a 4-4-2, he encourages his wide players to float into midfield and assist with both defensive and creative duties. Spanish midfielder Cani pops up in a variety of positions, but they will miss the input of Santi Cazorla after he was sold to Malaga.
Much will depend on the goal-scoring abilities of Italy international Giuseppe Rossi up front, while front partner Nilmar has the class to flourish in the Champions League.
MAIN MAN: Giuseppe Rossi
Huge sighs of relief could be heard around Castellon as the transfer window slammed shut at the end of August and Villarreal's star turn, Rossi, was still on board on the Yellow Submarine.
This one-time Manchester United starlet was linked with moves to some of the biggest clubs in Europe this summer and it is little wonder the vultures are swooping for a 24-year-old Italy international who smashed an impressive 32 goals in 56 club appearances last season. More of the same will make Villarreal a real threat in this Champions League campaign.
BIG SIGNING: Cristian Zapata
A relatively modest summer of spending at Villarreal was compensated by the retention of Rossi's services, yet coach Garrido is convinced the €7.5 million capture of Colombian defender Zapata can give his side additional steel at the back.
Arriving from Udinese, this 24-year-old was a transfer target for Liverpool before making the move to Castellon, yet Zapata made a poor impression in his first major game for Villarreal as his mistake handed Odense a first-leg lead in their Champions League play-off tie. Fortunately, his team-mates bailed him out with their triumph in the second leg.
RISING STAR: Mubarak Wakaso
Wakaso has taken a less than conventional route to the Champions League, with his emergence at Villarreal coming after a less than auspicious start to his career in Spain.
Sacked by lower league club Elche for alleged repeated breaches of club discipline, Villarreal scouts spotted the potential in this 20-year-old Ghanaian midfielder and handed him a contract. After making his first-team mark at the backend of last season, this confident left footer is now dreaming of glory against Europe's best.
THE X FACTOR: Nilmar
A Brazil international who is blessed with an array of silky skills, Nilmar has enjoyed more success during his second spell in European football after a disappointing stint at Lyon between 2004 and 2006.
After returning home to play for Corinthians, many cynics suggested he would be tossed onto the pile of Brazilian protégés who failed to live up to their billing, yet he has been a big hit since joining Villarreal in 2009 and has built up a fine strike partnership with the prolific Rossi.
FLAW IN THE MAKE-UP: Villarreal rely on Rossi and Nilmar to fire their engines and the lack of quality back-up is likely to become an issue for coach Garrido as his squad prepares to take on a heavy Champions League workload. What happens if one or both of the star duo are out injured? It is a prospect Villarreal dare not contemplate.
The summer sales of Santi Cazorla and Joan Capdevila - two of Villarreal's best players last season - confirmed that this club are paupers compared to many of their Champions League rivals in Group A. Many suspect they will not have enough class to survive at this level.
WHAT THEY SAY: "There was a lot of talk that I would be leaving Villarreal this summer, but I'm not thinking about Juventus or any other clubs now," Villarreal star man Rossi says. "I'm at a club looking forward to Champions League football and this is all I care about now."
VERDICT: A Europa League spot in the second half of this season may be the most realistic target in a devilishly tough Group A.
Status: 3rd in Premier League
Nickname: The Citizens
THE RECORD: Making their first appearance in the Champions League, big spending City are one of the dark horses to go all the way and lift the trophy. The club's finest hour in UEFA competitions came more than four decades ago, when they lifted the European Cup Winners' Cup in 1970.
TACTICIAN: Roberto Mancini
Many media pundits were predicting Mancini was on borrowed time as he struggled to ignite City midway through last season, yet a late flourish saw his team storm to third place in the Premier League and end a 35-year wait for major silverware with victory in the FA Cup Final.
"Winning the first trophy was important because this is what everyone spoke about at City, but being in the Champions League may be even more important," Mancini believes. "This competition could put City onto a different level in the eyes of football fans around the world."
THE GAMEPLAN: Mancini's latest spending splurge saw him add a host of additional attacking talent to his ranks. City have now banished the 'dour and negative' tag levelled at them last season and begin life in the Champions League with arguably most potent line-up of goal scorers in this season's competition.
A side featuring Sergio Aguero, Carlos Tevez, Mario Balotelli, Samir Nasri, David Silva and Edin Dzeko will score goals against any opposition, with City's flair up front backed up by the solid defensive midfield base provided by Nigel De Jong, Gareth Barry and, to some extent, Yaya Toure.
MAIN MAN: Sergio Aguero
One of the most wanted hit-men in world football finally sealed his big-money transfer away from Atletico Madrid in July as £38 million of City's unlimited supply of cash secured them the Argentine's services and he has the class to take the Champions League by storm this season.
The pace and clinical finishing ability Aguero brings to the party adds so City's embarrassment of riches and he should be able to work successfully with the likes of Dzeko, Balotelli and his compatriot Tevez. "You can only be excited by the project City are putting together and that's why I decided this was the club for me," said the son-in-law of Argentine legend Diego Maradona shortly after signing. "I don't think I will be disappointed."
BIG SIGNING: Samir Nasri
Arsenal fought long and hard to hang onto French midfield maestro during the summer, but City's cash spoke in the end and Mancini will benefit from the input of a proven Premier League and Champions League performer in Nasri, who shouldn't take long to settle in his star-studded line-up.
"This team is still coming together, but it feels like we can only get better with the quality of the players being signed," said Nasri, who pushed to end his stay at Arsenal for three months before his move to Manchester was secured. "This club can win any competition this season, including the Champions League."
THE RISING STAR: Mario Balotelli
It has been said that this maverick Italian is something of a 'pet project' for boss Mancini, with his eccentric ways tolerated by his compatriot on the touchline even though many observers have suggested the City manager would have an easier life if he offloaded this former Inter Milan frontman.
Balotelli's occasional flashes of brilliance are contrasted with more frequent infuriating displays, though Mancini feels he can extract some magic out of this raw Italian international, whose reputation as a dressing-room trouble maker is apparently set in stone.
THE X FACTOR: Carlos Tevez
No-one expected Tevez to start this season as a Manchester City player as he made it clear that he was determined to leave the club for family reasons, yet there were no takers for this highly-paid £40 million striker and it means he may play a crucial role in a Champions League campaign that he did so much to secure last season.
He may be unhappy in Manchester, but Tevez will give his all to the City cause if called upon, as this terrier of a striker does not know the meaning of playing with the handbrake on. A class act on the field, his regular career moves do little to banish the notion that his handlers are obsessed with making money from their star client.
FLAW IN THE MAKE-UP: There are question marks over City's back line and while the arrival of Gael Clichy from Arsenal in the summer should help their cause, it remains to be seen whether the likes of Joleon Lescott and Micah Richards are up to the job at Champions League level.
A lack of Champions League nous must also be an issue; while Mancini's players are experienced at the top level of the game, they have not played together in Europe's premier competition and may take time to find their confidence.
WHAT THEY SAY: "Being in the Champions League is a massive boost for the club and it was the priority above everything else last season," City assistant coach David Platt said. "Now we get our chance against Europe's best. This is what City have been working towards for the last few years."
VERDICT: Expect a stunning debut season for City, with a semi-final spot a possibility.
Status: 3rd in Serie A
Nicknames: Azzuri (The Blues)
THE RECORD: Napoli's finest hour in European competition came as the great Diego Maradona led them to UEFA Cup glory in 1989 and their long-awaited return to the continent's elite competition is setting pulses racing in Naples.
Their fine achievement in claiming a top-three finish in Serie A last season earned them a direct passage to the Champions League and they could emerge as a dark horse.
TACTICIAN: Walter Mazzarri
This shrewd touchline operator has done a fine job at Napoli since replacing former Italy boss Roberto Donadoni in 2009, with his work capped off by his appearance in this season's Champions League.
Having previously coached Livorno, Reggina and Sampdoria, he is relishing the chance to take on a tough opening group in Europe's top competition. "To have the strongest team in Germany (Bayern Munich) and the most potent English side in our group (Manchester City) makes this a tough challenge," he says. "It will be very difficult for us, but also exciting."
THE GAMEPLAN: A solid back three is led by club skipper Paolo Cannavaro, with the experienced Hugo Campagnaro and Miguel Angel Britos giving him able support as they aim to keep the door closed at the back, yet it is in the attacking third that a Napoli side featuring a host of South American stars can unsettle the best.
Using wing-backs to add some width and attacking pace, Swiss midfielder Gokhan Inler was a key addition in the summer and his classy input should assist the dangerous Marek Hamsik. Argentine Ezequiel Lavezzi and Uruguayan Edinson Cavani provide the cutting edge up front, along with loanee Goran Pandev.
MAIN MAN: Marek Hamsik
This Slovakian playmaker is one of the most talked about midfielders in the game, so Napoli did well to fend off high-profile interest in his services during the summer transfer window.
The fact that they could offer him a Champions League stage to perform on meant the task of keeping Hamsik in Naples was made a little easier, with his commitment to the cause assured. "There was some talk about Milan being interested in me, but leaving Napoli right now was never my intention as this club is on the up," he says. "I look at our Champions League group draw and say, 'Okay, let's not fear our opponents. This is the challenge we wanted'."
BIG SIGNING: Gokhan Inler
Napoli needed to make a statement as they prepared for their return to the Champions League and they did just that by luring this talented Switzerland international from Serie A rivals Udinese during the summer.
"This move is the pinnacle of my career and the chance to play for Napoli in the Champions League is a prospect to relish," he says. "Everyone wants to play in this competition and we have to believe in ourselves if we want to succeed."
RISING STAR: Federico Fernandez
The deal to bring this Argentina international from Estudiantes to Napoli was agreed some time ago, but visa issues halted his arrival until this summer.
He arrives with the delicious prospect of Champions League football on the agenda and, while this promising centre-back is unlikely to be a first pick for Napoli from the start of their European campaign, he is a great option to have on the bench. "We believe Federico has the potential to be a top player and the interest in him confirmed that other clubs agreed with our assessment," Napoli coach Mazzarri said.
THE X FACTOR: Goran Pandev
A few eyebrows were raised at Pandev's loan move from Inter Milan to Napoli and it may be that this experienced Macedonia international is a valuable wildcard for coach Mazzarri as he looks to find a winning formula in the Champions League.
"To join a club that is so excited to be part of Europe's top competition for the first time in many years makes this a great adventure for me," he says.
FLAW IN THE MAKE-UP: Napoli drew the short straw as they were thrown into a group with Bayern Munich and Manchester City, and the suspicion is that the Italians needed a more sedate opening to their first Champions League campaign.
Retaining the services of star men Hamsik and Lavezzi gives them a chance to cause a few shocks, but they need to ensure they don't suffer from an inferiority complex on the biggest stage. Much will depend on whether their attacking ambition can keep out the potent firepower that will be coming at them at the other end.
WHAT THEY SAY: "We have a chance to put ourselves firmly into the history of this club by succeeding in the Champions League and then they will talk about this team alongside the one Maradona led all those years ago," Napoli skipper Paolo Cannavaro says. "Maradona is the biggest figure in this history of this club, but this new team has the chance to follow in his footsteps."
VERDICT: A desperate group stage draw means a Europa League spot may be the best Napoli can hope for.