Our expert bloggers will give their thoughts ahead of each game, so as Bosnia-Herzegovina take on Argentina in Group F, Sasa Ibrulj (Bosnia) and Sam Kelly (Argentina) are your guides.
What's at stake?
Sam Kelly: These sides have only met twice before -- and never competitively -- so there's not much of a rivalry to speak of. The head-to-head is currently 2-0 in Argentina's favour, with seven goals scored and none conceded. The last time they played was a friendly in the USA in November, which Argentina won 2-0 using a similar 5-3-2 system to the one they've employed in training before this match. Of course, as one of the pre-tournament favourites and an eternal heavyweight, it's Argentina who have all the pressure to get off to a good start.
Sasa Ibrulj: Playing their first-ever World Cup match against one of the best teams in the world -- what can go wrong for Bosnia-Herzegovina? After years of struggling in mediocrity, the Dragons have finally reached the world stage. The celebration in Sarajevo after they beat Lithuania in the last match of the qualifiers, when more than 50,000 people went out on the streets and had a parade for the team, proves that for this country, just being in Brazil is equal to winning the title.
Of course, the expectations back home -- and among the players -- are bigger than just being tourists, but all the pressure is on Argentina. This should be the easiest match for Bosnia.
SK: Argentina have a few players who can hold their own when it comes to good passing and attacking flair. But let's face it, while my pre-tournament blogs about the importance of Angel Di María and Sergio Aguero are worth bearing in mind, there's only one man we can seriously mention here.
Lionel Messi is about to begin his third World Cup; his first as an undisputed centrepiece under a proper manager, and he has a point to prove. One match isn't going to make or break his tournament but he'd certainly love to get off to a good start, as would his legions of fans around the world.
SI: The whole world will talk about Edin Dzeko and Miralem Pjanic, but the Bosnians need their defence to provide the X factor. Muhamed Besic, the Berlin-born 21-year-old defender, has been converted to a holding midfielder and could be crucial to their hopes of stopping Argentina's attack.
SK: It's easy to pick out the opposing centre-forward, but it's especially so when he's just a season like the one Manchester City's Dzeko has just had. A solid one-goal-in-two striker, he's managed slightly more than that for his country, and his aerial presence could allow the Bosnians a chance to test Argentina's weakest link -- the wide positions in defence, particularly Marcos Rojo on the left -- in their very first match.
SI: Was the answer ever this obvious? Messi´s motivation is huge; he wants to show the whole planet that he is capable of working his magic in Argentina´s shirt.
Their team look impressive -- especially up front -- but Messi remains their number one, and a lot depends on him. Some suggest he needs to win the World Cup to be considered the greatest-ever footballer, and he has the ability to do that.
Fear is a good word for it.
SK: Di María versus Haris Medunjanin should be interesting. If Medunjanin can keep up with him and successfully shackle him, it will go some way to cutting off the fluidity between Argentina's midfield and strike force, which could be even more important unless Gonzalo Higuaín is passed fit to start.
This looks unlikely at the time of writing and although the two up front will be Messi and Aguero -- a scary proposition for opponents, true -- it is not an ideal combination if Argentina find themselves having to bypass midfield and look long.
SI: Dzeko versus Ezequiel Garay. The Dragons will not have many chances but Dzeko will have to take the best out of the ones they create. With Bosnia-Herzegovina probably being forced to sit deep and Dzeko isolated up front, his movement will be crucial if they want to create any danger.
SK: As they did in November, I think Argentina can win this one by a couple of goals. I'll go for 3-1. They look motivated, disciplined and happy together, and Bosnia-Herzegovina have the not inconsiderable task of having to work out how to defend against Messi, who didn't play the friendly in St. Louis last year.
SI: I wouldn't be a proper Bosnian-Herzegovinian if I didn't believe the team could surprise one of the best in the world. Argentina have rarely impressed in their opening World Cup matches, but they have not lost or drawn since defeat to Cameroon at Italia 1990. Even if my only argument here is that they have to slip at some point and the pressure is on them, I will stay an optimist and believe in a 1-1 draw.