Status: 4th in Premier League
Nickname: The Gunners
THE RECORD: A near miss in the 2006 Champions League final against Barcelona is the closest Arsenal have come to lifting the ultimate prize in European football, with heartache becoming an unwanted theme for Arsene Wenger and his players in the years since.
Arsenal have been winners in European competition, with their 1993-94 triumph in the Cup Winners' Cup Final against Parma coming courtesy of a goal from striker Alan Smith.
TACTICIAN: Arsene Wenger
Wenger's status as a living legend at Arsenal is under serious threat as he heads into his 14th successive Champions League campaign, with his stock falling at an alarming rate after six successive seasons without a trophy.
The most successful manager in Arsenal history points to his side's sustained presence in Europe's elite competition as evidence that he is still bringing a measure of success to the club. However, Wenger's remaining supporters may turn their back on the Frenchman if he falls short again this season and such a demise would be a sad epitaph for a coach who has brought so much joy to this club down the years.
THE GAMEPLAN: Wenger's passion for beautiful football helped to establish his legend at Arsenal, but the players he has assembled at seem incapable of bringing him the trophy success he craves using a progressive 4-2-3-1 formation.
Losing creative masters Cesc Fabregas and Samir Nasri cemented the perception that the tide has turned decisively against Wenger and he has to hope Champions League group stage rivals do not successfully employ the negative, counter-punching tactics that have proved successful against Arsenal in domestic competitions.
MAIN MAN: Robin van Persie
So often hailed by Wenger and his admirers as one of the finest strikers in Europe, Van Persie's flaky fitness and his tendency to slip off the radar when his team need him most means the Dutchman has plenty to prove this season.
The successor to Fabregas as Arsenal skipper, it's clear that Wenger is placing a bulk of his expectations for this season into the hands of the 28-year-old Dutchman. "Everyone is very negative about Arsenal right now, but let's see where we are by Christmas and make some judgments then," Van Persie says. "Maybe people will change their views if this starts to win games."
BIG SIGNING: Per Mertesacker
Wenger's critics have been urging the Arsenal boss to invest in a proven powerhouse defender for many a year and he bowed to the pressure when he signed this highly experienced German international from Werder Bremen for €8 million on transfer deadline day in August.
Never mind his lack of pace or his tendency to make the odd mistake, Mertesacker's presence at the heart of a notoriously brittle Arsenal back line will improve their hopes of ending an enduring problem when dealing with set-pieces into their box. After too many years of mediocrity, the arrival of this brand of centre-back is long overdue.
RISING STAR: Gervinho
Wenger has long focused the majority of his transfer activity on the French market, so it was no surprise to see him return to his homeland during the summer to secure the services of this tricky winger from Lille in a £10.5 million deal.
At the age of 24, Gervinho is something of a late bloomer at Champions League level, with his pace and trickery on the flank giving Arsenal a much-needed creative boost. "It has long been my dream to play for Arsenal and now the moment has come," Gervinho says. "This club should be winning trophies and we can do it this season."
THE X FACTOR: Mikel Arteta and Yossi Benayoun
Panic buys or inspirational signings on transfer deadline day? Time will tell whether Wenger's last-gasp rush to snap up Spanish midfielder Arteta in a £10 million deal with Everton and Israeli playmaker Benayoun on a season-long loan from Chelsea will fill the gaping void left by Fabregas and Nasri.
If the new-boys are an instant success for the Gunners, the gloom that has descended over Arsenal in the last few months could begin to lift. Alternatively, Wenger's misery will mount if Arteta and Benayoun turn out to be second-rate replacements for the departed world-class duo.
FLAW IN THE MAKE-UP: Mertesacker needs to be the answer to a defensive line that has cracked under pressure time and again in recent years, and Wenger has already moved to switch to a zonal marking system in his bid to stem the flow of goals conceded from set-plays.
Arsenal need to transform the Emirates Stadium into a cauldron on Champions League nights. As the departed duo of Fabregas and Nasri recently commented, the relative new stadium lacks the soul of Highbury and the team need some success to help the stadium find its identity. The last thing Arsenal need is their own fans turning against them at a moment when vocal support is required more than ever.
WHAT THEY SAY: "The signings Wenger made in the summer, albeit a little later than he should have done, give Arsenal something fresh to work with and I think they could surprise a few in the Champions League this season," upbeat former Arsenal striker Charlie Nicholas says. "Losing Fabregas and Nasri was a massive blow, but I can see a light at the end of the tunnel now. Arteta is a great buy for Arsenal."
VERDICT: Arsenal should have enough to get through this group stage, but don't expect them to go too much further.
Status: Second in Ligue 1
Nicknames: L'OM, Les Phoceens
THE RECORD: The only French club ever to win the Champions League, OM's moment of triumph took place on May 26, 1993 in Munich, as they defied the odds to beat AC Milan 1-0 thanks to a Basile Boli header. That victory more than made up for the bitter disappointment of two years earlier when they dominated the European Cup final against Red Star Belgrade, only to lose out in a penalty shoot-out. They have twice progressed beyond the initial group phase of the Champions League in the new millennium, reaching the round of 16 last term.
TACTICIAN: Didier Deschamps
France's World Cup-winning captain in 1998 has had his fill of success in the Champions League, leading OM to glory in 1993 and also coaching Monaco to a surprise runners-up spot in 2004, with his team losing 3-0 in the final to Jose Mourinho's FC Porto. In charge at Marseille since July 2009, he was widely-tipped to be on the verge of quitting the Stade Velodrome this summer, only to be persuaded otherwise by the removal of chairman Jean-Claude Dassier. An improved new contract and enhanced powers seem to have placated this respected coach.
THE GAMEPLAN: As one might expect from a former gritty midfield warrior, Deschamps is far more interested in efficiency and results than marks for artistic impression. So while his OM can on occasion lack for fluidity and technical pizzazz, they are rarely devoid of energy and passion. When they up the tempo, they are irresistible, yet critics would suggest they have a tendency to keep the handbrake on. Likely to go with a 4-3-3 formation, Deschamps will be looking for wingers Mathieu Valbuena and Andre Ayew to provide the penetration and ideas on the flanks. Morgan Amalfitano, a summer signing from Lorient, should add more poise and passing ability in the creative department.
MAIN MAN: Loic Remy
Marseille's top scorer last term with 17 goals, the French international striker combines elegance, pace, intelligent movement and lightning reactions in the box. Bought a year ago for €15 million from Nice, his medical appeared to indicate a heart defect, but he was given the green light to continue with his career following further tests.
Remy was a contemporary of rising stars Karim Benzema and Hatem Ben Arfa at the Lyon academy and now features alongside Benzema in the French national team front-line.
BIG SIGNING: Alou Diarra
After trying and failing last year to recruit the powerfully-built Bordeaux defensive midfielder, Deschamps finally got his man this summer, sealing a €5 million deal for the 30-year-old. His athleticism and ball-winning power should help OM immeasurably and he is no mean leader either, having served as the skipper of Bordeaux and the French national team. Strangely for someone of his calibre, Diarra failed to make any impact whatsoever during spells at Bayern Munich and Liverpool. A barely-used member of the French squad which came runners-up at the 2006 World Cup finals.
RISING STAR: Andre Ayew
The son of three-times African Footballer of the Year and OM legend, Abedi Pele, the 21-year-old winger has been on the fast-track to stardom in the last 12 months, performing with distinction for Ghana at the 2010 World Cup and establishing himself as a Marseille mainstay last term. Equally at home carving out chances as finishing them with aplomb, his career took off the season before last while on loan at Arles-Avignon, whom he helped win promotion to the top-flight.
THE X FACTOR: Mathieu Valbuena Known as 'Le Petit Velo', this diminutive wide man's dynamism, speed off the mark, dribbling skills and never-say-die attitude have made him a huge crowd favourite at the Stade Velodrome. No cause is ever lost as far as Valbuena is concerned. A surprise inclusion in the French squad for the World Cup in South Africa, he has his critics as many observers deeply resent his flair for diving and winning penalties and free-kicks. He has not always had the smoothest of relationships with coach Deschamps.
FLAW IN THE MAKE-UP: Despite the arrival in the off-season of full-back Jeremy Morel (ex-Lorient) and central defender Nicolas Nkoulou (Monaco), OM's rearguard remains as vulnerable as it was last season. They have to quickly find the antidote for the inexplicable capacity for crass individual mistakes and sloppy marking at set-pieces. Another question mark hovers over the commitment and focus of star Argentine midfielder Lucho Gonzalez. He had hoped for a fresh start elsewhere (Arsenal), but ultimately there were no takers. The overwhelming impression is that Didier Deschamps still does not know what his best formation is.
WHAT THEY SAY: "Nothing puts more of a spring in the step of OM than the prospect of high-level European football," says ex-Marseille star Manuel Amoros. "We're in something of a group of death (Arsenal, Dortmund and Olympiakos), but I trust Didier Deschamps to make his team more solid and better prepared for these encounters."
VERDICT: Droit au But (Straight for Goal) is the Marseille motto. Straight for a group stage exit might be the most probable outcome for Deschamps' men this season.
Status: Greek champions
Nickname: Thrylos (The Legend)
THE RECORD: The first Greek team to play in European competition - a Champions' Cup tie against AC Milan back in 1959 - the Piraeus club enjoyed their finest hour in the Champions League in the 1998-99 season as they progressed to the quarter-final stage, where they lost 3-2 on aggregate to Juventus.
Their success that season was built on their excellent home form, winning all three first phase matches in their backyard (Dinamo Zagreb, Ajax and FC Porto).
TACTICIAN: Ernesto Valverde - a one-time tricky little winger with Espanyol, Barcelona and Athletic Bilbao - has transformed himself into a cool, composed and highly-successful touchline string puller. This is Valverde's second stint at the Olympiakos controls as after leading them to the Greek title in 2009, a contractual dispute with the board led to his surprise departure. Just 15 months later and he was back, immediately leading the red-and-white stripes to yet another domestic championship.
Valverde has suffered the heartache of penalty shoot-out defeat in a European final. First, while playing for Espanyol against German side Leverkusen in the 1988 UEFA Cup, then as the Espanyol coach, when his side succumbed to Sevilla in the 2007 final of the same competition.
THE GAMEPLAN: In common with so many of his counterparts from Spain, Valverde's top priority is to dominate possession - keeping the ball the circulating left and right and playing in small triangles - before launching fast-paced raids into enemy territory. Not surprisingly for an ex-winger, he is especially keen on exploiting the flanks, where up-and-coming Greek star Ioannis Fetfatzidis and Albert Rieira occupy vital creative roles.
Whether it be in a 4-4-1-1 system or a 4-2-3-1, Olympiakos like to press as high up the pitch as possible and, on winning the ball back, invariably look to veteran Argentine playmaker Ariel Ibgaza to set their attacks in motion. The leader of the back-four is the vastly-experienced Swede Olof Mellberg.
MAIN MAN: Kevin Mirallas
This 23-year-old Belgian front-man was the club's top scorer last season with 14 goals. As much as his clinical finishing, coach Valverde loves the versatility Mirallas offers, his ability to operate in any number of positions: solo leader of the line, second striker, right-winger or attacking midfielder.
Initially brought on a season-long loan from French club St Etienne last year, Mirallas settled in so quickly in Greek football that Olympiakos were quick to offer him a permanent contract. A graduate of the Standard Liege academy and a Belgian international at every level from Under-17 upwards, the future looks bright for this Champions League hopeful.
BIG SIGNING: Ljubomir Fejsa
A promising young defensive midfielder signed from Partizan Belgrade this summer in a €3 million deal. Over the years, Olympiakos have been well served by Serb stars such as schemer Predrag Djordjevic and striker Darko Kovacevic and the hope in Piraeus is that the 22-year-old will prove equally valuable.
A Serb League winner in each of the past three seasons, he made his full debut for his country in a Euro 2008 qualifier at home to Kazakhstan.
RISING STAR: Ioannis Fetfatzidis
The recent decision by the Olympiakos board to increase the buy-out clause of their diminutive winger or playmaker to €12.5 million was logical. The slightly-built 20-year-old is the most naturally-gifted Greek prospect for many a long year and while the Piraeus board accept that the 'Hellenic Messi' is bound to depart at some point, they hope to hang on to him for another year or two at least.
Up to now, coach Valvderde has been careful not to over-extend his prodigy, starting him one week, putting him on the bench the next, but the boy wonder is likely to be asked to turn on the style more regularly this season. Fetfatzidis has been with Olympiakos from the age of 13.
THE X FACTOR: Marko Pantelic
This impish striker may not be the most disciplined or conventional of pro footballers, but the 32-year-old is worth his weight in gold as a genuine penalty area hit-man. Olympiakos is the 12th club of a long and eventful career and while he can infuriate with his diva-like behaviour, he has the ability to deliver at the perfect moment.
Pantelic joined Olympiakos on a free transfer from Ajax a year ago, with Paris Saint-Germain, Lausanne, Red Star Belgrade and Hertha Berlin listed among the former employers of this Serbian international.
FLAW IN THE MAKE-UP: Dominating of the Greek scene is hardly the best way to gear up for the far more demanding Champions League and Olympiakos have find a way of ditching the Jekyll and Hyde personality, the competitiveness at home and capitulation away from Greece.
They have a reputation for beginning a game with all guns blazing, only to gradually fizzle out and there are question marks hovering over new keeper Franco Costanzo can be erratic.
WHAT THEY SAY: "A group featuring Arsenal, Dortmund and Marseille is super tough," concedes ex-Olympiakos defender Grigoris Georgatos. "This team may have the pride, the will and some good players, but don't have the game-changers of the best sides in Europe. It will be tough for them to make the impression they want."
VERDICT: Crash and burn seems to best sum up their chances.
Status: Bundesliga Champions
Nickname: BVB (Ballspiel Verein Borussia - Ball Game Club Borussia)
THE RECORD: Dortmund have twice gone all the way in Europe, beating Liverpool 2-1 in the final of the 1966 Cup-Winners' Cup at Glasgow's Hampden Park and 31 years later overcoming Juventus 3-1 in the Champions League showpiece in Munich.
The abiding image of that 1997 final was provided by fledgling attacking substitute Lars Ricken, who just one minute after coming on for Stephane Chapuisat, sealed his team's win with a delightful chipped finish.
TACTICIAN: Jurgen Klopp is a charismatic, emotional and unconventional young boss who has worked a sporting miracle since arriving in Dortmund from Mainz three years ago, transforming a team which was barely treading water in the Bundesliga into German champions.
A long-serving utility player with Mainz, he combines extraordinary powers of motivation, attention to detail and intense will-to-win.
Klopp's behaviour on the touchline is best described as volcanic and every goal his side scores has him celebrating with fists pumping. He was a popular TV pundit at World Cups and European Championships.
THE GAMEPLAN: At the heart of their modus operandi
Usually employing a 4-2-3-1 system, Borussia are especially strong in possession in the middle of the field and simply love to penetrate on the flanks, where starlets Kevin Grosskreutz and Mario Gotze invariably run riot.
MAIN MAN: Kevin Grosskreutz
A local lad who used to stand on the terraces at the Westfalenstadion, this all-action left-sided midfielder represents the emotional heartbeat of the team. Clearly overjoyed to be playing for the side he adores, he is full of running from first minute to last and always ready to rally the troops. Last season, the 23-year-old was sensational, calmly tucking away eight chances and making another seven.
In his third season in the Borussia first-team, Grosskreutz joined them in 2009 from second division Rot-Weiss Ahlen and made his full debut for Germany in May 2010 in a friendly against Malta.
BIG SIGNING: Ilkay Gundogan
Dortmund fans feared the worst when brilliant young midfield regulator Nuri Sahin chose to leave the German title-winners for Real Madrid in the close season, but they need not have worried. In Gundogan, a €4 million summer signing from Nurnberg, they have a fine replacement, a 20-year-old who can work defensively and pass and probe with the very best.
Born in Gelsenkirchen, the home town of Dortmund's arch rivals Schalke, he could have chosen to play international football for Turkey, the country of his parents, yet insists he is only interested in wearing the colours of the Nationalmannschaft and his first call up to the Germany squad came at the start of this season.
RISING STAR: Mats Hummels
Bayern Munich officials must regret the day they declared this cultured young centre-back surplus to requirements back in 2008, first allowing him to go on loan to Dortmund, then telling him not to bother coming back. Since that brush-off, Hummels has gone from strength to strength and so high has he climbed that he is now on the verge of a regular spot in the German national team.
For all his power in the tackle and in the air, what really makes him a special talent is his composure on the ball. Thanks to his excellent distribution and willingness to step into midfield, he is often the man to get Borussia moving.
THE X FACTOR: Mario Gotze
The son of a data technology professor at Dortmund University, the teenage attacking midfielder took the Bundesliga by storm last term and now finds himself dubbed Germany's answer to Messi. A livewire mixture of mesmerising dribbling, imaginative use of the ball and dead-eye finishing, he could quite easily be overwhelmed by the hype yet remains remarkably level-headed.
On Dortmund's books from the age of nine, he recently won his first senior cap for Germany in a friendly against Brazil, marking the occasion with a goal. Could his next step be a starring role in the Champions League and Euro 2012?
FLAW IN THE MAKE UP: Some have questioned whether a youthful Borussia have sufficient know-how to compete at Champions League level. Although they swept all before them in the Bundesliga last season, it's worth noting that they were not nearly so effective in the 2010/11 Europa League, failing to progress beyond the group phase.
Their all-action playing style is not exactly economical on the body and they can be picked off by more tactically-astute and pragmatic opponents. Paraguayan striker Lucas Barrios apart, they lack prolific goal getters.
WHAT THEY SAY: "The two things I noticed about Dortmund last season was the fun they had on the pitch and the great confidence they displayed," says Arsenal's Germany defender Per Mertesacker. "They really enjoy putting the opposition under pressure and believe they can run any opponent into the ground. They are young and have no fears or complexes and will make an impact in the Champions League."
VERDICT: They have a tough opening group but write off the Dortmund perpetual motion masters at your peril.