Some will be challenged to overcome personal hurdles—figuratively and literally—while others will stare down the mounting pressure of victoriously representing their respective country.
To these athletes, second place is the first loser.
Will they be able to pick up where they left off, and answer the critics?
Five Olympic rings present them with the opportunity to.
Tyson Gay, in all likelihood, is the fastest man in America. But what about the world?
Odds are, probably not.
But there is a sub-story underlying the 100m dash that he and Usain Bolt will compete in.
Bolt owns the world record for the event, recording a 9.58 in 2009 at Berlin. Gay shattered the American record with a 9.69.
However, Usain Bolt has only faced defeat one time since 2008, and Tyson Gay was the reason.
There have been a few minor setbacks for Gay, though: a torn labrum, ankle injury, groin surgery, strained hamstring, a hampered adductor, and "inflammation near his pubic bone."
Injuries have become commonplace in Gay's road to Olympic gold, and he's racing against Father Time.
Fans would be hard-pressed to find an Average Joe walking down the street that could name another duo.
The two ascended to the peak of their fame after winning gold medals in both the 2004 (Athens) and 2008 (Beijing) Olympics. The pair also dominated the FIVB World Championships in 2003, 2005 and 2007.
However, the two separated after the 2008 Olympic Games to focus on family life, with no foreseeable plans of making another run.
Four years later, and the fearless tandem have reunited to reclaim their Olympic reign.
Behind them? Misty May-Treanor and Kerri Walsh.
Marta is the best female soccer player in the world; it's as irrefutable as the sky is blue.
However, one player can only do so much as part of a whole team. Scoring opportunities are scarce, especially against defensive-minded adversaries.
No. 10 will certainly pad her individual stats, but Brazil expects championships. Although Marta will leave every drop of sweat on the field in attempting to bring one home, there are three teams currently ranked above the soccer powerhouse that resides in South America.
If Marta helps captures the gold for Brazil, Japan, Germany and the USA will have to collapse.
Don't expect to that happen.
Michael Phelps has gills.
Or at least, his 2008 Olympic performance would lead one to believe so.
He sported a record eight gold medals around his neck before he was finished in Beijing, which is exactly why his 2012 outing could be considered disappointing to fans.
Laszlo Cseh, a fellow swimmer from Hungary, has acquired a medal in every tournament that he has participated in for the past 10 years. After witnessing Phelps showcase his skills in 2008, Cseh's conviction will be stronger than ever.
Phelps set the bar at a height that was previously undiscovered.
The only thing more difficult than climbing Mount Everest, is climbing it twice.
Brit Jessica Ennis has the pressure of a nation on her shoulders.
She competes in the heptathlon, consisting of: 100m hurdles, high jump, shot put, 200m, long jump, javelin throw, and the 800m run.
When The Sun interviewed the diversely talented 26-year-old, she was quoted as saying, "Dobrynska is the favorite now and you can never write off Chernova. She will be one of the favorites as well."
Ennis is the cover-girl for the 2012 Olympics, considering that the games are being held on home turf in London.
But can she overcome her two recent rivals that have detoured her quests for gold?
Only time will tell.