Michael Phelps stakes his claim to be the ultimate Olympian on Wednesday, swimming two finals in an hour as he bids to overtake an elite group including Mark Spitz and Carl Lewis on a record nine career golds.
China and the United States, already fighting an epic battle at the top of the medals table, face each other in one of the Games' blue riband events, the women's team artistic gymnastics.
The Phelps phenomenon, though, is dominating the headlines in the first week of the Games. On Wednesday he starts with his signature event, the 200 metres butterfly.
Then comes the 4x200 freestyle relay, an event the Americans won in 2004 and traditionally stamp their authority on.
Anything less than two golds would be a major surprise.
After equalling his own Olympic record of the day before in the 200 butterfly semi-final on Tuesday, the 23-year-old is taking everything in his own, laid-back style.
"I just wanted to swim my race and set everything up for tomorrow," he said. "I have to go back and do all that stuff to set myself up for the perfect swim."
"All that stuff" brought Phelps his third gold, and his third world record, of the Games on Tuesday, with an imperious victory in the 200 freestyle.
That in turn brought him level with compatriots Lewis and Spitz, "Flying Finn" distance runner Paavo Nurmi and Soviet gymnast Larysa Latynina on nine golds.
Latynina and fellow Soviet gymnast Nikolai Andrianov hold the record for the most medals in all, with 18 for women and 15 for men respectively, but two golds for Phelps would let him stake an impressive claim for the title of the greatest Olympian.
It would also bring him more than halfway towards surpassing Spitz's other record, seven golds in a single Games.
His fellow-Americans might have brushed China aside in a basketball match earlier in the week, but they are so far trailing the hosts 13 golds to seven in the medals table.
Few contests may be as close, or as closely watched, as the women's team gymnastics. The Americans, who dethroned the Chinese as world champions in 2007, had arrived with high hopes of giving their country their first Games team title on foreign soil.
But two of their gymnasts, Chellsie Memmel and Samantha Peszek, are both nursing ankle injuries and they were outclassed in qualifying.
Their best hope is that the Chinese fail to cope with an unaccustomed early start, after the event was switched to the morning to catch the prime-time American television market. Some face wake-up calls as early as 6 a.m..
"I'm tense about it because I'll be lying awake worrying about it all night," said Chinese gymnast Cheng Fei. "I'll be very tired in the morning."
Beijing's changeable weather seems to have dominated the road race cyling, more than a third of the men's field failing to finish on Saturday, including fancied German Stefan Schumacher, who said pollution had given him a "very, very bad headache".
The women were drenched on Sunday, upsetting many of the field, including veteran Olympian Jeannie Longo from France.
So both men and women are wondering what to expect when they compete in the time trials at the Great Wall on Wednesday.