Top 14 youngest billionaires under 40
Besides Facebook's CEO Mark Zuckerberg, the names that cracked Forbes' list of 400 wealthy Americans before the age of 40 are unrecognizable ? for now.
They range from wildly successful tech industry entrepreneurs with newfound riches to the heirs of massive fortunes.
Click through the gallery to see which billionaires have rocketed to the top of the ladder of success.
All figures in U.S. dollars.