News It has been called the biggest multi-competition sports event in the USA All eight days are already sold out, with more than 200,000 tickets snapped up The world's greatest ever Olympian will be competing – and he's not guaranteed to win It's the 2016 US Olympic Swimming Trials, which start this Sunday (26 June) in Omaha, Nebraska and run until 3 July Bar the Olympic Games themselves, the US trials may be the toughest competition in world swimming The USA have dominated the pool for decades; at London 2012, the Americans went home with 31 medals (including 16 golds), more than three times as many as no 2 nation China The trials are the only selection event for the country's Olympic swimming team of about 50 men and women  In most events, only the top two finishers will make it onto the Rio team In Omaha, there will be no bronze medals for coming third The stakes could not be higher for the 'Big Four' of USA swimming; multiple Olympic and world champions Michael Phelps, Ryan Lochte, Missy Franklin and Katie Ledecky A model of sustainability, Olympic Aquatics Stadium for Rio 2016 Games is unveiled For Phelps, who won six medals in London to bring his total to 22 (18 of them gold), these will be his fifth and final trials Phelps, who will turn 31 at the end of June, came out of retirement to compete at Rio 2016 but is adamant that he will not be going to Tokyo 2020 Ominously for competitors, Phelps, who became a father in May, says he is feeling better than ever going into the trials   "I’m a lot more relaxed I am enjoying this experience a lot more leading up to these Olympics,” Phelps told usaswimming org “I am just doing what I love I’m never too uptight, and we always keep it really light in the pool, really light in workouts When it is time to swim, I need to put my game face on, and I’m ready to go ” Michael Phelps, winner of 22 Olympic medals in swimming Phelps is scheduled for five events in Omaha: the 100m and 200m butterfly, the 200m individual medley, and the 100m and 200m freestyle He is also likely to make the relays based on his times in the freestyle events, where he is not a contender for individual medals USA swimming superstars poised to battle for places at Rio 2016 Olympic Games For Ryan Lochte, who won five medals in London (two of them gold), Omaha will be his fourth Olympic trials Although Lochte hasn't made a public announcement, they look likely to be his last; the swimmer will turn 32 before Rio 2016 begins Lochte has entered six events at the trials: 200m and 400m individual medley, 200m and 100m freestyle, 200 backstroke and 100m butterfly As with the men's events, the women's swimming competition will be dominated by two established Olympic stars: Missy Franklin and Katie Ledecky Franklin, who at the age of 21 has already won four Olympic golds, will be competing in the 100m and 200m freestyle as well as in the 100m and 200m backstroke events, in which she is the reigning Olympic champion Franklin competed at the 2008 trials at just 13 before bursting onto the international swimming scene in 2012 as a 17-year-old, winning Olympic gold and setting a world record in the 200m backstroke "I feel stronger and fitter than ever before, and I’m so excited to see what this summer has in store," Franklin, known as 'Missy the Missile', said ahead of the trials She has even said that for swimmers who get through the US trials, the Olympic Games can seem like "a piece of cake"   Katie Ledecky was even younger than Franklin when she won 800m freestyle gold medal at London as a 15-year-old In Omaha, Ledecky is slated to swim in six events and looks an almost certain qualifier in the 100m, 200m, 400m and 800m freestyle She already holds the world records in the 400m and 800m and is the reigning world champion in 200m, 400m, 800m as well as in the 1500m, which is not an Olympic event   A new generation But there is much more to this USA swimming team than the Big Four, and Omaha next week will be a chance for new stars to shine   Young, up-and-coming names to look out for at the trials include Maya DiRado, who starts as a favourite to win the 200m and 400m medleys and make it to her first Olympic Games Simone Manuel, DiRado's teammate at Stanford, looks a strong bet for the 50m and 100m freestyle races The two women train together at university; to judge by this video, the US dive team can sleep easy In the men's events, a more established star will be enjoying his moment in the spotlight next week Current Olympic champion Nathan Adrian is already looking forward to defending his 100m freestyle title in Rio and adding to his haul of four Olympic medals (including three golds)   However, Adrian will not have it all his own way, as a new generation of male swimmers is on the verge of making an Olympic breakthrough In the sprint events, 19-year-old Caeleb Dressel looks like a real threat, especially after breaking the American record in both the 50 yard and 100 yard freestyle As well as Dressel, the trials will thrust into the spotlight a number of outperforming teenagers who look poised to lead the next generation of American swimming For 17-year-old Michael Andrew, who turned professional at just 14, these will be his first trials A gold medallist at the junior world championships, Andrew has entered five races in Omaha He's watching his diet closely in the countdown to race time In the women's trials, 18-year-old distance specialist Becca Mann is another one to watch A screenwriting student who has already published a novel, Mann is already an experienced open-water swimmer and currently looks the most likely to finish second behind Ledecky in the 800m freestyle An even younger performer in the men's competition will be Reece Whitley, who at just 16 is a towering 2 03m in height (6 foot 8 inches)  At the 2015 national championships, Whitley recorded the same time as Phelps in the 200m breaststroke – aged just 15  Whitley has already established a healthy rivalry with Andrew For some of the younger swimmers, Omaha and Rio 2016 may well be coming too early in their careers, However, it may only be a matter of time before they add to the USA's record haul of Olympic medals Just as nobody imagined that Mark Spitz's achievements at Munich 1972 would ever be bested until Phelps arrived on the scene, one of today's youngsters may one day put Phelps himself into the shade