Young Money: Billionaires Under 40
Facebook execs, Under Armour founder among world's richest young people.
Billionaires Under 40: Facebook Execs, Under Armour Founder
Frustrated with sweating through cotton T-shirts, former University of Maryland football player Kevin Plank developed a moisture wicking material that became Under Armour. Now a staple piece for almost any athlete's uniform, Under Armour exploded into in an appeal clothing brand that includes pants, jackets, shoes and gear. Plank, 39, is estimated to have a net worth of $1.1 billion. (John McDonnell/Washington Post/Getty Images)
