Messi scored 275 goals for Barcelona and 45 for Argentina. Mostly he celebrated goals by aiming fingers and looking to the sky. Wonder why? Here is explanation.

Messi already started playing football with 5 years. His grandma Celia by most cases drive him to the stadium.
She was first person to notice Lionel's skills in football, so she drive him to the stadium, where he training. When Messi was 11 years old grandma died.

Messi said:

"She supported me on trainings. I would if she could be with me today. Unfortuanely she died before she saw me with success. That hurts me the most."

She noticed skills which little Lionel had in football, his passion, love and talent.

She would be very proud if she see how Messi, which had problems with physical grow, become one of best footballers today, and possibily one of best in history of this sport.

Respect for Messi.

Trailer for Messi - The Movie (can't wait to watch it)

Respect. After all these years he still does it.

275 goals only in the League, 397 goals in total ( friendlies and pre-season not included in official competitions )...
Legend.

I've heard a lot good of his grandmother before, how he was a major aspect behind Messi's football in his youth, as you mentioned the things she did for Lionel. Really sad he didn't see the success.

I heard the story before, I knew his gesture dedicates to his grandmother. I thought it was really cool (before that I thought it was just religious thingy that he does that)

Respect to him and his grandmother.