Please keep safety in mind when you see pictures of this sort.
Check the minimal road clearance on the bike. With a very low center of gravity most experienced riders can do it on a RACING TRACK.
Another thing to remember is that most of the MotoGP and MotoCross riders learned to ride bikes under the age of ten, yes that's TEN years old. They started racing at 12 to 15 years of age, in races for those age groups or 50cc or 60cc classes.
Gabor Talmacsi, ex-125cc World Champion, "started riding motorcycles aged four in a mini-bike school run by his father".
About the current 125cc World Championship leader, Mike DI MEGLIO: "The French youngster turned 15 on the eve of the first test of the 2003 and made his 125 World Championship debut that year on an Aprilia".