Between now and July 2, the top American athletes in four of the Olympics’ most popular sports — diving, track and field, swimming and gymnastics — will battle each other for a chance to compete at London 2012. With thousands of athletes vying for a few select spots, the Olympic trials are arguably tougher gauntlets to run than the Games themselves. They are also where relatively unknown contenders can rise to prominence and where world record holders can be sent packing. Many of the trials will air on the NBC Sports Network. Here are some of the athletes to watch.