BMX (Bicycle Motocross) is a form of cycling on specially designed dirt bikes which usually have 20 inch wheels. BMX or Bicycle Motocross orignated from racing bikes over dirt jumps, this is known as BMX racing. Tricks were also developed using these bikes and this evolved into Freestyle BMX. Freestyle BMX includes five distinct disciplines. These are Street, Park, Vert, Dirt, and Flatland. These usually involve highly technical movements of the bike in different ways over varied terrain. BMX Racing has just become an official Olympic event at the Beijing Olympic games held in 2008. This is a long way from when the sport was started by kids in United States in the early 70's, who imitated their motocross heroes on their road bicycles by riding around the motocross circuit.