Today, Ken Griffin is the Chairman, President and CEO of Citadel Investment Group, the Chicago-based hedge fund that has grown into a global investment giant with offices in New York, London, Hong Kong and Tokyo, handling more than $20 billion in investment capital. A teenage computer whiz from Boca Raton, Florida, Griffin started his first investment fund in his Harvard dorm room, writing his own software to execute a novel arbitrage strategy for trading convertible bonds. A year after graduating, he founded Citadel, with $4.6 million in capital. The new firm grew explosively, nimbly...