On September 15, 1997 Larry Page and Sergey Brin, two 24 year-old Stanford University students, registered the domain name of google.com. The word is a variation of 'googol,' which refers to the number 10 to the power of 100, a term popularized by US mathematician Edward Kasner. Page and Brin incorporated Google one year later, on September 7, 1998, in a household garage in northern California. Soon after its launch this search engine has become the most popular Internet search engine in the world outside of China, Japan and Russia, handling more than 500 million visits a day. In 2006 Google bought YouTube, the largest and most popular video exchange website, and soon after bought DoubleClick, one of the Internet's most powerful ad services. Google also launched free e-mail - Gmail. Today Google shares are valued at 525 dollars, and Google has a stock market value worth of 164 billion dollars.