A day after Mark Zuckerberg took his company, Facebook, public, the CEO updated his relationship status to "married."

Zuckerberg, 28, and his longtime girlfriend Priscilla Chan exchanged vows at a small ceremony in their backyard attended by less than 100 guests in Palo Alto, Calif., on Saturday.

Guests thought they were coming over for a surprise party to celebrate Chan's graduation from UCSF medical school, where on May 14 she received her degree in pediatrics. However, Zuckerberg and Chan had been planning the wedding for more than four months, according to a source authorized by the couple.

Zuckerberg designed Chan's wedding ring, a simple ruby sparkler, himself.

Guests dined family-style on food from the couple's favorite restaurants, Palo Alto Sol and Fuki Sushi. For dessert, they had Burdick Chocolate "mice" – whimsical chocolate treats made in the shape of mice – which the couple had on their first date.

The couple, who met while attending Harvard before Zuckerberg – who is now worth more than $19 billion – started Facebook, have been dating for nine years.

Zuckerberg, the subject of the movie The Social Network, had been in the news all week for the highly-anticipated stock offering of his company.

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