The referee has just (accidently) floored Chelsea's Erin Cuthbert...

Barcelona's Aitana Bonmati takes the first shot of the day after turning Sjoeke Nusken in the box.

However, she gets under the ball and sends it wildly over the bar.

Early roars from the Chelsea crowd as Lucy Bronze unleashes Johanna Rytting Kaneryd down the right.

The next attack sees Sandy Baltimore carry the ball into the box.

Sonia Bompastor promised an attacking approach from her side and they've started brightly.

Karen Bardsley
Former England and Manchester City goalkeeper on BBC Radio 5 Sports Extra

Milie Bright is going to have to keep the morale up, be the voice and the leader by example on the pitch. We have seen her pick players up and put them back in positions.

She will have to be an absolute 10/10 like the rest of her Chelsea team mates today to make sure they get up to the levels they think they are capable of.

And we're off!

Barcelona, playing in a distinctive hi-viz green, get this second leg under way.

We're moments away from kick-off at Stamford Bridge, so what better time for a completely unscientific poll?

Can Chelsea complete an unlikely comeback? Thumbs up for yes. Thumbs down for no.

Here's a quick reminder of how the two sides are lining up at Stamford Bridge.

Image source, BBC Sport

Image source, BBC Sport

BBC Radio 5 Sports Extra

Coverage of today's game at Stamford Bridge has just got under on BBC 5 Sports Extra, with Vicki Sparks and former England goalkeeper Karen Bardsley on commentary.

You can tune in via your radio and on BBC Sounds, or by clicking the 'listen here' button at the top of this page.

Neil Johnston
BBC Sport at Stamford Bridge

Music - including Madness and Blur - has been turned up to 10 as kick-off approaches while Blue is the Colour - Chelsea's anthem - has been booming out of the speakers.

To the left of the press box is a pocket of Barcelona fans who are clapping, waving flags and generally have a great time.

There's about 100 of them right now.

Will they still be in a party mood at full-time?

Chelsea

Chelsea manager Sonia Bompastor speaking to TNT Sports: "In the game against Man City [in the quarter-finals], we were losing but we came into the second leg with the right mentality and I expect that again today. We are going to finish today with no regrets.

"I'm so proud of my players. We have already achieved a lot but today, we must give our all on the pitch. This opportunity today is for our team to show our best and perform at our best level.

"When you are facing challenges, you need to embrace them. That's my mentality and the mentality I want my players to have. If we can score the first goal, anything can happen."

Image source, Getty Images

Since 2009-10 when the UEFA Women's Cup was rebranded as the Women's Champions League, no side has overturned a three-goal deficit to win on aggregate.

However, Chelsea captain Millie Bright says "nothing is impossible" as her side attempt to do exactly that against Barcelona.

Bright did not hold back in her assessment of Chelsea's performance in the first leg, criticising their mentality and defending, but called on her teammates to "bounce back" and "show what Chelsea are about".

"It's a big ask, but going into any game and trying to perform against a top team is a big ask," Bright said.

"Nothing is impossible within football or in sport if you have the right mentality, the right attitude.

"The biggest thing to come off the first leg is we didn't present ourselves in the right way. We didn't play as Chelsea with our core values and represent the badge, the kit. That's where we were really disappointed.

"Defending has been something we've been really good at throughout the season. We've been really strong and really hard to beat, hard to score against. We weren't at our best but we've got an opportunity to bounce back and show ourselves."

Neil Johnston
BBC Sport at Stamford Bridge

Have I mentioned how good the weather is at Stamford Bridge?

Well, a couple of TV presenters and cameramen got a real soaking a little earlier after being caught out by the Stamford Bridge sprinklers which were suddenly activated while they were filming pitchside.

They've watered the pitch on what feels like the warmest day of the year.

Jen Beattie
Former Arsenal defender

Crazier things have happened in European football lately. We've all seen how even 3-0 deficits aren't enough. But don't get me wrong, when you get to semi-finals, that's a big gap. The quality is so much higher, and it's a huge task for them.

There are big players in that dressing room. They can do it. I'm an optimist.

Chelsea

Chelsea boss Sonia Bompastor says her side are "ready" for the challenge awaiting them at Stamford Bridge and has promised to "attack the game" and "take risks" as they bid to keep their quadruple dreams alive.

The Blues must overturn a three-goal deficit against defending champions Barcelona if they are to reach the Women's Champions League final after losing the first leg of their semi-final 4-1.

"We'll need to score for sure. So this is the mentality we are going to attack the game with," Bompastor said.

"We'll go for it. I think this is part of the club's DNA but it's also out mentality. We'll be playing at home and we'll try to do our best to be able to be in a position to score goals.

"But we also know it's really important not to concede. That's the big challenge but we're ready for it.

"We'll have to take risks to be able to score. I know within my squad, I have a lot of talent and quality. The players who will start the game will have to show that talent tomorrow. But I know we are capable of doing that."

Image source, Getty Images

Neil Johnston
BBC Sport at Stamford Bridge

They had sold 20,000 tickets for today before the first leg and Stamford Bridge could have been looking at an attendance close to sell-out had Chelsea not lost 4-1 in Catalonia.

Instead they're expecting something in the region of 30,000.

That's not bad at all and with blue skies over Stamford Bridge, there could be plenty of last-minute walk-ups.

Image source, Getty Images

Barcelona are on course for a third successive Women's Champions League title, something only Lyon (who won five in a row from 2016 to 2020) have previously achieved.

With three titles, they're the third-most successful side in the competition's history, behind Lyon (eight) and Eintracht Frankfurt (four).

Manchester City are the only side to get the better of Barcelona in this season's competition, beating them 2-0 in the opening round of group fixtures.

Since then, Barcelona have scored 40 goals in eight matches - the most in the competition - with Claudia Pina (nine) and Ewa Pajor (six) sitting first and joint-second in the overall goal-scoring charts.

At the opposite end of the pitch, they have conceded just six goals, with only Lyon boasting a better defensive record.

Image source, Getty Images

Chelsea manager Sonia Bompastor says this match will be the "biggest challenge" of her career.

The Blues must overturn a three-goal deficit at Stamford Bridge after suffering a 4-1 defeat in the first leg.

Bompastor, who twice won the competition as a player, is no stranger to beating Barcelona, having coached Lyon to victory in the 2021-22 final, but knows her side have a difficult task against "one of the best teams in Europe".

"When I was [Lyon] manager in 2022, we just beat Barcelona in the final and it was a huge challenge, but I think this one will be probably the biggest one in my career as a manager," she said.

"We need to turn the three goals up and also, we're playing against one of the best teams in Europe, if not the best team. It will be difficult.

"We will need to try everything and this is why we're talking about having a good mentality. I think the right mentality going into the game is to give everything, give our whole, and not to have any regrets at the end of the game."

Ellen White
Former Manchester City striker on Women's Football Weekly

It's an uphill battle [for Chelsea]. If you were take 2-1 back to Stamford Bridge, I think I would be laughing. 4-1 is a lot.

Chelsea can score a lot of goals, but can they not concede? Barca are going to score goals, they've got it in their locker.

I think they do believe they can [win]. It's just whether they can score enough goals and not concede against Barcelona. I'm not quite sure that they could do that.

Neil Johnston
BBC Sport at Stamford Bridge

The sky is as blue as Chelsea's shirt.

It really is a glorious day at Stamford Bridge but the big question is: will Chelsea turn it around and stage a glorious comeback?

Chelsea

Prior to last Sunday's defeat in Barcelona, Chelsea had only lost once all season.

However, while Sonia Bompastor's side are not used to losing, they have already completed one comeback in the Women's Champions League this season.

In the quarter-finals, they overturned a two-goal deficit against Manchester City to win 3-2 on aggregate and captain Millie Bright believes that experience will help them against Barcelona.

"It's confidence, just reflection on when we played City at the Bridge and what we did in that game, especially in the first 45 minutes. It could have been more than 3-0," Bright said.

"We know what we're capable of. We just need to be at the races and be the first ones on the pitch demanding that intensity, setting the tone. It's our home turf and we need to be the ones leading that."