Brendan McCullagh: Make no mistake, Everton are contenders for this trophy, really impressed by their performance tonight.
Nick: Young Boys can't play against English opposition - First Liverpool thrash them now Everton's turn.
A great win for Everton, can their Premier League rivals follow suit? Liverpool and Tottenham kick-off their last-32 games against Besiktas and Fiorentina respectively in just under 15 minutes.
Europa League holders Sevilla are yet to lose at home to a German side in European competition as they prepare to welcome Borussia Monchengladbach in the round of 32 while Dutch champions Ajax prepare to face Polish opponents for the first time in Europe as they take on Legia Warsaw .
Villarreal are unbeaten in three European home games this season whilst tonight's opponents Salzburg have won all three of their Europa League away fixtures this season.
Russian side Dynamo Moscow will look to extend their 10-game unbeaten run in Europe as they travel to Anderlecht while French Cup winners Guingamp have made it to the knockout stages of European competition for the first time and prepare to host Dynamo Kiev in Brittany.
Presenter, BBC Midlands Today
European nights at Celtic Park this season have lacked the sparkling intensity of recent seasons - the Europa League will do that. But this evening feels different. The prospect of facing a genuine European giant - albeit a slightly diminished one - has increased the sense of anticipation about the stadium and it could be reminiscent of a big Champions League night.
Everton come forward through Steven Naismith in pursuit of a fifth. He passes to Luke Garbutt, who then loses possession. That's probably the last attack of the game.
Three minutes of added time and Everton are looking good to head back home with a three-goal cushion ahead of the second leg.
Worth remembering that Young Boys were ridiculously strong at home. They had scored 13 goals and conceded just one in their five previous Europa League matches in Bern this season and have been well beaten tonight.
The legends of '67 will be hoping that, tonight, Celtic Park will be celebrating the heroes of 2015.
That's Romelu Lukaku's last action of the game and he gets a deserved round of applause as he heads off the pitch with three goals to his name.
Christian Atsu, who was player of the tournament at the Africa Cup of Nations, is on in his place. He scored an absolute belter at the Afcon, worth a look if you have not seen it!
Steven Naismith is down clutching his leg after overstretching to challenge for possession. The result may be good, but some of these injuries may be a concern for Roberto Martinez.
But Steven Naismith is nails. He runs off his injury and moments later Everton are so close to a fifth. Romelu Lukaku powers away from the home defence and tries to lift the ball over Yvon Mvogo, who makes a great save.
Looks like Christian Atsu, fresh from returning from the Africa Cup of Nations where he helped Ghana to the final, is about to come on.
Yellow card for Romelu Lukaku. Not sure what for, even he doesn't seem to know what for as he shrugs his shoulders at the referee in disbelief.
Another change for Young Boys as Tauljant Sulejmanov replaces Renato Steffen for the final 12 minutes.
Scrap that, they get forward as Romelu Lukaku goes for a fourth but he is offside as he heads wide from a cross.
Alexander Gerndt again has a chance, but the effort is blocked for a corner. Everton are not being adventurous now they are down to 10 men.
Kazim Kazim-Richards (formerly Colin in his days in English football) has bagged an equaliser for Feyenoord in Roma , cancelling out Gervinho's first-half strike to leave the scores locked at 1-1 at the Stadio Olimpico, while Hulk has given Zenit St Petersburg a 1-0 lead at PSV Eindhoven .
A brace from Bas Dost has put Wolfsburg 2-0 up against Sporting Lisbon and a Kenneth Petersen own goal has increased Club Brugge 's lead to 3-0 at Aalborg while Jaba Kankava and Ruslan Rotan have put Dnipro 2-0 up at home to Olympiakos .
Torino still have a 2-1 advantage over Athletic Bilbao while Napoli have not yet extended their 3-0 lead at Trabzonspor in the second half.
A fine introduction to the game by Alexander Gerndt as the former Swedish player of the year meets a cross to volley a shot straight at Tim Howard. A little more to the left or right and that would have been 4-2.
Romelu Lukaku should have his fourth! Substitute Luke Garbutt crosses low from the right and the bounce on the artificial pitch catches out the Young Boys defender but also surprises Lukaku, with the ball bouncing off his foot and wide from barely four yards out.
Antolin Alcaraz is on for James McCarthy as Robert Martinez makes his second change. Young Boys also make a change as Milan Gajic is replaced by striker Alexander Gerndt.
Celtic start with the same XI as the one that began the match against St Johnstone on Saturday. That means European debuts in a Celtic jersey for Gary Mackay-Steven and Stuart Armstrong and Leigh Griffiths keeps his place up front.
From my discussions with an Italian colleague earlier, it would appear the only slight surprise in the Inter Milan line-up is the inclusion of Rodrigo Palacio ahead of Mateo Kovacic.
Celtic XI : Gordon; Matthews, Denayer, van Dijk, Izaguirre; Brown, Bitton; Mackay-Steven, Johansen, Armstrong; Griffiths.
Inter Milan XI : Carrizo; Campagnaro, Ranocchia, Juan Jesus, Santon; Medel, Guarin, Kuzmanovic; Shaqiri; Palacio, Icardi.
Penalty to Young Boys as John Stones brings down Guillaume Hoarau. Stones is also red carded. Big chance for the hosts to get back into this....
Tottenham boss Mauricio Pochettino has left in-form striker Harry Kane on the bench as he hands Roberto Soldado a chance to impress in attack as part of six changes from the side which lost 3-2 at Liverpool last time out.
Ben Davies and Federico Fazio come in for Eric Dier and Danny Rose in defence while Andros Townsend, Nacer Chadli and Paulinho come in for Ryan Mason, Mousa Dembele and Erik Lamela in midfield.
Fiorentina coach Vincenzo Montella gives a Europa League debut to Egypt winger Mohamed Salah, who has joined on loan until the end of the season from Chelsea as part of the deal which took Juan Cuadrado to Stamford Bridge.
Manchester City defender Micah Richards, who is on a season-long loan with the Florence club, is named among the substitutes for the visitors at White Hart Lane.
Tottenham XI : Lloris, Walker, Fazio, Vertonghen, Davies, Bentaleb, Paulinho, Chadli, Eriksen, Townsend, Soldado.
Fiorentina XI : Tatarusanu, Rodriguez, Basanta, Savic, Pizarro, Joaquin, Fernandez, Valero Iglesias, Pasqual, Salah, Gomez
Freddy Howard: Important Everton leave Switzerland so they have an easy second leg - gives them the opportunity to concentrate on vital Premier League matches.
Matt Austin: I think the reason Everton look better tonight is because in the league teams have learned that sitting deep nullifies us. Not so in Europe.
Romelu Lukaku completes a great night as he scores his third of the game and it is a typical Lukaku strike. He charges away on the attack, gets beyond a defender to leave him one-on-one and he sidefoots home.
A few Young Boys players seem unhappy, though, as it appeared some had stopped as James McCarthy was down injured and needed treatment.
Bryan Oviedo limps off and, as expected, on comes Luke Garbutt.
It looks like Bryan Oviedo's game is over. He has injured his hamstring having bumped Renato Steffen off the ball to prevent him crossing. Luke Garbutt is instructed to warm up quickly.
A chance for Everton as Bryan Oviedo sends a cross into the area, Steve von Bergen tries to head the ball away but only as far as Kevin Mirallas, unmarked on the right side of the area, but he lashes his shot wide.
Ross Barkley is booked but it could have been much worse. The Everton midfielder was down on the ground after a challenge and got knocked in the head by the trailing foot of Sekou Sanogo. Barkley gets up and pushes Sanogo and out comes the yellow card and the referee screams a warning at Barkley.
Tim Howard's first action of the second half is to help a speculative cross-shot over the bar. It looked like it was going over, but he couldn't be too sure. The subsequent corner comes to nothing.
Liverpool striker Daniel Sturridge makes his European debut for the Reds having missed the whole of their Champions League campaign through injury.
Reds boss Brendan Rodgers makes one change from the side which beat Crystal Palace in the FA Cup with Jordon Ibe in for the suspended Lazar Markovic. Raheem Sterling is back on the bench following a recent foot injury.
Besiktas coach Slaven Bilic includes Demba Ba in his starting line-up after the striker shook off a slight knock. It will be the first time Ba has faced Liverpool since scoring for Chelsea last year in a win which damaged the Reds' title hopes.
Liverpool XI : Mignolet, Can, Skrtel, Sakho, Allen, Henderson, Moreno, Ibe, Coutinho, Lallana, Sturridge.
Besiktas XI : Gonen, Kurtulus, Franco, Gulum, Motta, Hutchinson, Kavlak, Tore, Sosa, Sahan, Ba.
Can the second half live up to the first? Will Romelu Lukaku complete his hat-trick?
We are back under way.
Striker Harry Kane starts on the bench for Tottenham against Fiorentina.
Tottenham XI : Lloris, Walker, Fazio, Vertonghen, Davies; Bentaleb, Paulinho; Chadli, Eriksen, Townsend; Soldado.