Teams held moment of silence across Europe.
Lionel Messi unveils his new boots to the fans.
Full highlights between Celtic and Barcelona.
Lionel Messi gives Barcelona a 1-0 lead against Celtic.
Take a look back at all the best action from Matchday 4.
Messi explains Argentina's players are not speaking.
Full highlights between Manchester City and Barcelona.
Messi gives Barcelona a 1-0 lead against Manchester City.
Leo Messi scored his second consecutive hat trick in UCL.
Lionel Messi extended Barcelona's lead against Man City.