Champions Brazil, patiently watching and waiting for the first four days of the World Cup, launch their attempt to win the competition for the sixth time on Tuesday.
Elsewhere, debutants Togo, involved in a farcical merry-go-round of firing, appointing, dismissing and re-hiring coaches, play their first World Cup match against South Korea, while former winners France take on dangerous outsiders Switzerland.
Record-chasing Brazil meet Group F rivals Croatia in the opening match in Berlin's Olympic Stadium, hoping they will eventually return there for the final on July 9.
If they beat Croatia, the South Americans will become the first team to win eight successive matches in the finals, following their seven victories in 2002.
Ronaldo, who has 12 goals in the finals, also needs three more to overtake West German Gerd Mueller's all-time record total from 1970 and 1974.
Although Brazil are favourites to win the World Cup, coach Carlos Alberto Parreira is concerned about the strength of opposition in Europe.
"It will be very difficult to win a sixth World Cup," Parreira said at a news conference at the stadium after taking training on Monday. "The European teams are at home here. They just have to take a bike or a bus and they're here in Germany. They're in their own house."
Togo's house has resembled one in which every family member is having a row, coaches coming and going like teenagers slamming the door and leaving home.
But with Otto Pfister back in charge after quitting last week, the Africans are now ready to take on South Korea in a Group G encounter in Frankfurt.
The whole mish-mash was prompted by a pay dispute involving the Togo players, who have lost the support of fans back home and need to score an unlikely win to regain self-respect.
Group G favourites France meet Switzerland for the 36th time in their history but for the first time in the World Cup.
The Swiss are looking to maintain their unbeaten run of games in 2006.
Monday's matches began with Australia scoring a spectacular 3-1 comeback win over Japan in Group F, with all three of their goals coming in the dying minutes.
In Group E, Czech Republic recorded a 3-0 win over United States and Italy got their World Cup underway with a 2-0 triumph over Ghana in Hanover.
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