Bone-smashing action, brutal finishes and fighters that leave it all in the cage. Mixed Martial Arts has exploded onto the scene to become one of the fastest growing sports in the world. MMA was born with one single, bloody question: Which fighting style is the toughest? To reach the top, a fighter must master various fighting techniques -- kickboxing, wrestling, jiu-jitsu and more -- and blend them together: The great Georges St-Pierre steamrolls through his opponents in the UFC, but in school he was mercilessly targeted by bullies, that is, until he learned karate; Most fighters respect their opponents, but they don't have to like them; some of the greatest rivalries of all time feature bad blood (and lots of real blood, too) -- Chuck Lidell vs. Tito Ortiz, Matt Hughes vs. Georges St-Pierre and Ken Shamrock vs. Royce Gracie; Before going on to have one of the greatest careers in MMA history, Randy Couture won a gold medal at the 1991 Pan American Games in wrestling; In the early days of the UFC there were no weight classes; in one match, a karate master was 400 pounds lighter and nine inches shorter than his sumo wrestler opponent, but the karate master still won; Legendary UFC hall-of-famer Royce Gracie was born to be a champion: his father and uncle invented Brazilian Jiu-Jitsu, an art that any self-respecting MMA fighter with a ground game must learn.