Bill Gross was famous during the Internet boom as the founder of Idealab, an "incubator" that hatched more than 75 companies. His best-known investment was GoTo.com, which created an online marketplace where advertisers bid for primacy in the results of Web searches--the innovation, now called "keyword advertising," that made Google wildly rich (with the all-important tweak that sponsored and algorithmically derived results should be clearly separated). GoTo.com (which became Overture Services) was sold to Yahoo for $1.6 billion in 2003.

Of course, Gross (and Idealab) never really went away. Among Gross's recent investments is eSolar, a TR50 startup of which he is chairman. The company hopes that with its technology, solar thermal energy--heat and electricity generated from sunlight using mirrors--will cost no more than coal-generated power. Jason Pontin, Technology Review's editor in chief, met with Gross at the 2010 annual meeting of the World Economic Forum in Davos, where eSolar was honored as a Technology Pioneer.