When Google hired Marissa Mayer in 1999, she was the company's 20th employee and its first female engineer. She went on to become the person responsible for designing and developing the attractive and easy-to-use search interface, and has launched more than 100 features and products on Google. She oversees many of Google's most-used features including Google Images, Google Maps, Google Earth, and Google Books. Mayer's work may be behind the scenes, but many recognize her power and her worth; Fortune named her one of the 50 Most Powerful Women -- at age 33, the youngest ever to make that list -- and Newsweek cited her as one of " the next generation of leaders in their fields." The ultimate test of her influence? Google her. You'll see half a million results.