Mark Zuckerberg, founder of social media giant Facebook, is one of the world's richest and most famous men.
As the billionaire celebrates his 30th birthday today, we share 10 surprising facts about the CEO.
1. He was raised by a dentist and a psychiatrist
Born in New York, Zuckerberg has three sisters, Randi, Donna and Arielle. His father is a dentist and his mother a psychiatrist.
2. He started programming when he was young
His father initially taught him about computers and programming but then hired a developer to tutor him. The developer, David Newman, labeled him a prodigy.
His father also enrolled him in a graduate course in programming while still in high school.
3. His first popular site breached security and violated privacy
While studying at Harvard, Zuckerberg built a "hot or not" website, called Facemash, that took online photos from facebooks of the college's Houses. Users were then asked to select which one they thought was "hotter". There was a massive backlash and Zuckerberg was banned from access to Harvard's internet and accused of breaching security and individual privacy.
Photo / AP
4. He is red/green colourblind
Zuckerberg suffers from red/green colour blindness, which means the colour he can most easily see is blue - no surprise then, that Facebook is blue.
5. He dropped out of Harvard to pursue his dream
Initially launched as Thefacebook, Zuckerberg developed a website for college students to connect. He moved to California and found an investor for his project. He purchased Facebook.com in 2005.
6 .The Social Network was a metaphor
Released in 2010, the film The Social Network had the strapline "You don't get 500 million friends without making a few enemies" and portrayed Zuckerberg in a less than flattering light.
When it won four Golden Globes awards in 2011, producer Scott Rudin acknowledged Zuckerberg saying, "I want to thank everybody at Facebook; Mark Zuckerberg for his willingness to allow us to use his life and work as a metaphor through which to tell a story about communication and the way we relate to each other."
Screenwriter Aaron Sorkin said, "I wanted to say to Mark Zuckerberg, if you're watching tonight, Rooney Mara's character makes a prediction at the beginning of the movie, she was wrong. You turned out to be a great entrepreneur, a visionary and an altruist."
7. He met his wife while queuing for the bathroom
Zuckerberg met Priscilla Chan at a party in his sophomore year and they soon began dating on and off. She was one of the first people to join Facebook in 2004 and moved in with him in 2010. The couple tied the knot in 2012 when Chan had finished medical school.
8. He's had several legal battles
Zuckerberg was a billionaire by the age of 23 and he has been accused of intellectual theft, blasphemy and failure to uphold a contract. His longest-running legal battle was with twins Cameron and Tyler Winklevoss who claimed that Zuckerberg had stolen their idea for Facebook. Zuckerberg countersued and they ultimately reached a settlement of $65 million in 2009. The pair were back in court in 2011 accusing Facebook of hiding information pertinent to the trial. Eventually they decided to not seek a Supreme Court review.
9. He sets himself a self-improvement goal every year
Each year, the Facebook billionaire sets himself a new challenge. In 2009, he wore a tie to work every day to show he was "serious" about his company. In 2010 he learned Mandarin (a language his Facebook profile says he can speak). In 2011 he only ate animals that he had killed himself and in 2012 his challenge was to code every day. In 2013 he challenged himself to meet a new person outside of Facebook every day. And this year? He has set himself the goal of writing at least one well-considered thank-you note every day via email or snail mail.
10. He has signed The Giving Pledge
In 2010 Zuckerberg, along with Bill Gates and Warren Buffet signed The Giving Pledge, which is a promise to donate at least half of their wealth to charity. Now there are some 122 billionaires who have signed the pledge. Facebook COO Sheryl Sandberg and her husband are the latest billionaires to sign the pledge, having done so last week.