Search giant Google is celebrating its 13th birthday. In keeping with tradition, it has posted a birthday Doodle with a cake, candles and balloons.

Google began in January 1996 as a research project by Larry Page and Sergey Brin when they were both PhD students at Stanford University in California.

According to Search Engine Watch, the exact date of Google’s birthday has changed and been debated a bit through the years. Google filed for incorporation on September 4, 1998, was established three days later on September 7, and the Google.com domain was registered September 15. All have been considered Google’s “birthday” at one point, but Google has officially chosen September 27 as their day.

Google doodles gained immense popularity over the past years reminding of news events, civic milestones, birthdays and important dates in history. Google created more than 900 doodles since 1998, with 270 of them running in 2010 and about 200 in 2011.

Google has acquired more than 100 companies over the past ten years. In August it announced its plans of acquisition of Motorola Mobility, the purchase marking the gian’t most expensive acquisition to-date at a staggering $12.5 billion.

In May 2011, unique visitors of Google surpassed one billion mark.