Key dates in the history of Facebook, which is celebrating its 15th anniversary in February:
JANUARY: Mark Zuckerberg, a 19-year-old computer whiz at Harvard University, begins working out of his dormitory room on an online network aimed initially at connecting Harvard students.
FEBRUARY: Thefacebook.com is launched by Zuckerberg and three Harvard roommates and classmates: Chris Hughes, Eduardo Saverin and Dustin Moskovitz.
MAY: Zuckerberg moves to Silicon Valley and decides not to return to Harvard for the fall semester.
JULY: The new company receives its first investment: $500,000 from PayPal co-founder Peter Thiel.
AUGUST: Thefacebook.com officially changes its name to Facebook.
FEBRUARY: Viacom offers to buy Facebook for $1.5 billion but is turned down.
SEPTEMBER: Yahoo makes an unsuccessful $1 billion bid for the social network. Facebook adds the "News Feed" and opens up to anyone over the age of 13.
SEPTEMBER: Facebook launches a $10 million fund to provide money to companies or individuals who want to build applications.
OCTOBER: Microsoft takes a $240 million stake in Facebook, which has 50 million members.
DECEMBER: Zuckerberg apologizes for "mistakes" in rolling out a new ad platform called Beacon that tracked purchases made by Facebook members and let their friends know what they had bought.
FEBRUARY: A $65 million settlement is reached with twins Tyler and Cameron Winklevoss over allegations that Zuckerberg stole their idea for Facebook while at Harvard. Facebook launches a Spanish site.
MARCH: Sheryl Sandberg, a top Google executive, is hired as Facebook´s chief operating officer. French and German Facebook sites are launched.
APRIL: Facebook dethrones MySpace to become the world´s most popular social networking website.
AUGUST: Facebook membership hits 100 million.
MARCH: Facebook launches its first mobile application.
MAY: Russian Internet company Digital Sky Technologies invests $200 million in Facebook.
DECEMBER: In one of many privacy flaps, activists ask the US Federal Trade Commission to look into whether Facebook deceived users over protection of their personal data.
MAY: Pakistan blocks access to Facebook over a competition encouraging users to post caricatures of the Prophet Mohammed.
JULY: Membership hits 500 million. Lady Gaga becomes the first with 10 million fans on Facebook, breaking the barrier a few days ahead of then-president Barack Obama.
OCTOBER: "The Social Network," David Fincher´s story of the origins of Facebook, hits movie theaters. Nominated for eight Oscars, it takes three: best adapted screenplay, original score and film editing.
DECEMBER: Time magazine names Zuckerberg as Person of the Year for "transforming the way we live our lives every day."
JANUARY: A private share offering raises $1.5 billion from investors and values Facebook at $50 billion.
FEBRUARY: Facebook announces plans to move from Palo Alto to a sprawling campus once home to Sun Microsystems in nearby Menlo Park.
SEPTEMBER: Timeline pages are introduced that let Facebook users turn their profiles into interactive digital scrap books that tell the stories of their lives.
NOVEMBER: Facebook agrees to tighten privacy policies and submit to external audits in a settlement with US regulators.
JANUARY: Facebook files for an initial public offering.
MAY: Some $16 billion is raised in the IPO, giving the company a market value of $104 billion. A hoodie-clad Zuckerberg remotely rings the Nasdaq bell from Facebook´s California headquarters on the first trading day.
AUGUST: Facebook closes a deal to buy the popular photo-sharing app Instagram for $1 billion
SEPTEMBER: Shares in Facebook slide more than 50 percent from the IPO price of $38 amid fears on growth and profitability, but the slump will prove transitory.
OCTOBER: Facebook membership tops one billion.
JANUARY: Facebook launches a "social graph" search engine to find posts on the network, in collaboration with Microsoft.
DECEMBER: Facebook is added to the Standard & Poor´s 500 index, which represents the largest publicly traded US firms. Video ads debut in Facebook feeds.
FEBRUARY: Facebook buys smartphone messaging platform WhatsApp in a cash and stock deal valued at $19 billion.
MARCH: Facebook buys virtual reality headset maker Oculus in a deal valued at $2 billion. Zuckerberg predicts VR will be the next major computing platform.
Facebook moves into its new Frank Gehry-designed headquarters in Silicon Valley, with a rooftop park and "the largest open floor plan in the world."
NOVEMBER: Facebook and other social networks are embroiled in controversy over manipulation of online platforms by Russia to sow division and sway elections.
JUNE: Facebook tops two billion monthly users.
SEPTEMBER: Facebook reveals hundreds of fake profiles evidently orchestrated by Russia bought ads to fuel political tensions ahead of the recent presidential election.
MARCH: Scandal breaks that British consulting firm Cambridge Analytica stealthily harvested personal data of millions of Facebook users and used it for political purposes including helping the campaign that resulted in the election of US President Donald Trump.
APRIL: Zuckerberg is grilled in US Congress over Facebook´s handling of user data and the social network being manipulated to undermine democracy.
JULY: Facebook´s value based on the price of its shares reaches an all-time high of nearly $628 billion.
JANUARY: As Facebook nears its 15th anniversary, Zuckerberg pledges "public discussions about the future of technology in society" in his latest effort to address heightened concerns about social media.