Stjarnan 1 Celtic 4 (1-6 agg): Scottish champions progress
Celtic came from behind to claim a 4-1 win over Stjarnan and seal a 6-1 aggregate success in the UEFA Champions League second qualifying round on Wednesday.
Leading 2-0 from the first leg at Parkhead, Celtic were always favourites to progress as the expense of the Icelandic champions.
But it looked as if the Scottish Premiership side were going to be in for a tough examination when Stjarnan took an early lead through Olafur Karl Finsen's low strike.
Forward Finsen capped off a free-flowing attack, but Celtic dominated proceedings thereafter and eventually levelled as their extra quality told.
Israel midfielder Nir Biton headed home from a corner before Charlie Mulgrew put Celtic ahead in the 49th minute, with Leigh Griffiths and Stefan Johansen rounding off the scoring late on.
Mulgrew collected the ball from Scott Brown and unleashed a shot past goalkeeper Gunnar Nielsen, ending the tie as a contest and setting up a third qualifying round meeting with Qarabag of Azerbaijan.
Stjarnan opened the scoring after just seven minutes as Finsen finished off a wonderfully worked team move.
Celtic still enjoyed the lion's share of possession and looked to have equalised in the 22nd minute through Dedryck Boyata, who bundled in on the rebound from a Johansen shot only to be flagged for offside.
But Ronny Deila's men did restore parity 11 minutes later when Biton capitalised on some poor defending to glance Johansen's right-wing corner into the net at the near post.
And Celtic almost completed the turnaround in the 36th minute, Stuart Armstrong shooting narrowly wide of the post from Gary Mackay-Steven's pass.
Just four minutes into the second half, though, Celtic did take the lead on the night and took an even firmer grip on the tie thanks to Mulgrew.
The Scotland international picked the ball up on the edge of the area and arrowed a shot into the bottom-right corner beyond a helpless Nielsen.
There were chances at both ends as the game opened up in the second half. Substitute Griffiths shot just beyond the far post for Celtic before Brynjar Gudjonsson and Finsen went close for the hosts.
Mackay-Steven and Nadir Ciftci spurned further opportunities for Celtic before Griffiths rolled the ball into an empty net and Johansen fired home a fourth to give the scoreline added gloss.