Conversation so far:
When did Donnie Yen start martial arts?
At a young age, Donnie Yen developed an interest in martial arts and began experimenting with various styles. Yen then started kung fu when he was nine.
Who trained Donnie Yen?
Donnie Yen's parents were concerned that he was spending too much time in Boston's Combat Zone. They sent him to Beijing on a training program with the Beijing Wushu Team.
How long did Donnie Yen train with the Beijing Wushu Team?
Two years
Are there any other interesting aspects about the Donnie Yen article besides his early years?
Donnie Yen's exposure to mixed martial arts (MMA) was heightened when he went back to the United States from 2000 to 2003.
How was Donnie Yen's exposure to mixed martial arts heightened?
While making his Hollywood debut, Donnie Yen took time off to learn various martial arts forms. When he returned to Asia, he implemented his newfound knowledge of MMA.

Question: What were the various forms?
Self-contained rewrite: What were the various martial arts forms Donnie Yen learned in his time off from Hollywood?