Barcelona took the advantage over Arsenal in their round of 16 clash at the Emirates on Tuesday night as they won 2-0 thanks to two goals from Lionel Messi.
The Gunners had a good chance in the first 10 minutes as Mesut Ozil found space down the left, but his cutback was behind Aaron Ramsey who scuffed his shot.
Barcelona started to get their passing game going and threatened through Neymar and Messi, yet Arsenal had the best opportunity to break the deadlock when Hector Bellerin's shot was deflected into the path of Alex Oxlade-Chamberlain who was six yards out. The England winger wasn't able to connect properly with his shot and it was blocked by goalkeeper Marc-Andre ter Stegen.
A Messi free kick hit the wall, then Oxlade-Chamberlain lost control on the break and was stopped by Javier Mascherano before he could square the ball to Olivier Giroud in the middle.
Just before half-time, Arsenal almost gave Barcelona a goal. Bellerin and Aaron Ramsey gave the ball away and Luis Suarez squared to Messi but Nacho Monreal made the tackle before the Argentine could shoot.
With seconds remaining, Suarez then met a Dani Alves cross five yards out but saw his flicked header sneak past the far post.
After the break, Barcelona had a chance within five minutes as Neymar broke free but Petr Cech came out quickly and blocked his low shot with his legs.
Oxlade-Chamberlain, unable to shake off his injury, came off for Theo Walcott and Barcelona continued to have the run of the game. Neymar should have done better with a header, while Messi was unable to get on the end of a low cross.
On the hour mark Arsenal came back into the game as Ozil broke away but could not find a red shirt with his cutback. Seconds later, Giroud got his head on the end of a cross which was well saved by Ter Stegen low down by his post.
Mertesacker threw himself in front of a Messi shot, then Suarez hammered a cross inches past the post as Neymar couldn't get on the end of it.
Barcelona then broke the deadlock in the 71st minute as Arsenal committed too many men upfield and Neymar, Suarez and Messi broke. Neymar broke free, squared for Messi who waited for Cech to dive before flicking the ball over him and into the net.
Barcelona could have doubled their lead as they broke ahead again, but when Neymar's effort was blocked it fell to Suarez who hit the post with his effort.
Messi, however, put the game beyond doubt as he slotted home a penalty. Just minutes after coming on as a substitute, Mathieu Flamini brought down the Argentine in the box and he picked himself up to coolly slot home.
Gerard Pique was booked late on, meaning he will miss the second leg through suspension, and Cech made a fine save from a Neymar header late on to keep the score at 2-0.