Meet Y Combinator's Bold Whiz Kid Boss Sam Altman is redefining the venture capital firm's identity and making bold moves. After one year on the job, has his strategy paid off?

Venture capital firm Y Combinator defied expectations when it replaced co-founder and longtime president Paul Graham with Sam Altman, the whiz kid behind social networking app Loopt. A year into his tenure, Altman continues redefining his firm's identity, making bigger and bolder bets on startups from across the spectrum. Meet the new boss.

It was mid-2012, and it was time for a change. Computer programmer and entrepreneur Paul Graham realized that Y Combinator, the influential Silicon Valley venture capital firm and seed-stage accelerator he co-founded in 2005, needed to expand its horizons to keep pace with the explosive growth of the global startup culture. Graham also recognized that he was not the one to spearhead this next phase in the firm's life cycle, so he began taking steps to relinquish his presidency and identify a successor.

Graham's search eschewed the usual suspects and zeroed in on Sam Altman, the twentysomething co-founder of Loopt, a location-based social networking app and graduate of Y Combinator's first-ever funding batch. After Loopt was acquired in 2012 by debit-card issuer Green Dot for $43.4 million, the Stanford-educated Altman launched early-stage venture fund Hydrazine Capital. It invested in startups like HR software provider Zenefits (now valued at $650 million) and DNA-printing tech developer Cambrian Genomics. He also was an angel investor in Y Combinator-backed companies such as digital payments juggernaut Stripe before joining YC in 2011 as a part-time partner.