A rare foray forward from Celtic comes to nothing and Barca break at lightning speed.

Neymar is played in on goal but Dorus de Vries stands up well to save from the Brazilian.

A corner is whipped in from the right and Ivan Rakitic volleys towards goal but the ball is cleared off the line by Kieran Tierney on the post.

Ten minutes to half-time. Can Celtic keep it at 2-0?

Barca look in the groove and that is a worry for Celtic.

Messi's clever inside pass finds Neymar in the box, he lays it off for Luis Suarez who just gets his angles wrong with an attempted chip over de Vries.

These short run-ups should be banned!

A really poor penalty from Dembele. He takes his time in the run up hoping Ter Stegen in the Barca goal will flinch but he doesn't and guesses right as Dembele puts his effort too high and too central.

A simple enough save from the keeper in the end. Huge chance gone for the Scottish champions.

Scott Sinclair slips it through to Moussa Dembele who is taken down by the keeper.

Dembele to take it.....

Tom English
BBC Sport Scotland at Camp Nou

Barcelona's speed of thought is extraordinary. We've seen it a million times but you can never tire of it.

They're three or four passes ahead of Celtic who are all about damage limitation now.     

Pat Bonner
BBC Scotland pundit at Camp Nou

"It's very difficult to keep possession. You can work hard but you need a breather and if you can't keep hold of the ball for more than a few passes, then it is very tough."

We are midway through the first-half and it has been every bit as challenging for Celtic as predicted.

Barca's crisp passing and exceptional movement are proving extremely difficult to combat.

However, aside from the goal, Celtic have defended pretty well up to this point. They'll have plenty more defending to do before this match is finished though.

Messi fizzes a dangerous ball across the face of goal but Luis Suarez just can't get on the end of it.

Celtic struggling to contain the Barca superstars but are hanging on in there.

Erik Sviatchenko makes a strong challenge on Ivan Rakitic on the edge of the area but the ball breaks to that man Messi. He nutmegs Nir Bitton and curls an effort that goes a couple of yards wide of the post.

Well the match has settled into the expected pattern with Barca zipping the ball about in front of the packed Celtic penalty area.

The Celtic defence can't take their eyes of Messi, Suarez or Neymar for a second. We've already seen what happens when they do.

That opener was Lionel Messi's 84th Champions League goal.

Simply extraordinary. 

Pat Bonner
BBC Scotland pundit at Camp Nou

"Celtic are watching the ball. You have to watch where the runners are coming from. It's about getting your body shape right, and watching where players are coming from. You have to match the runs. They can cut you right open because they are great passers."

Liam McLeod
BBC Sport Scotland at Camp Nou

"Once again Celtic cut up like ribbons at the back!"

It's another scary moment as Lionel Messi is put clean through on de Vries again, but mercifully for Brendan Rodgers' men the offside flag is raised.

It's a serious situation for Celtic already, although after the offside flag was raised Kolo Toure hilariously lashed the ball against his own post and out to safety.

Panic from the veteran defender or one of the greatest pieces of skill ever produced?