Key Twitter moments: The first tweet – In the early going, founders were using the vowel-free "Twttr" because they were focused on mobile and hoped to get the SMS shortcode 89887 (TWTTR). Unfortunately, according to co-founder Jack Dorsey, that was already owned by Teen People. This was his first tweet.
South by Southwest – Twitter was still a digital infant in March 2007, when the world's technorati descended on Austin, Texas, for the South by Southwest Interactive festival. According to its founders, Twitter traffic more than tripled that week. All those influencers went home and shared the glories of a service even some tech-savvy folks didn't quite understand at the time.
'Arrested,' then freed – With one word, U.S. graduate student James Buck set in motion the process that would eventually get him freed from prison in Egypt. He was arrested April 10, 2008, while reporting on protests in the city of Mahalla. His one-word tweet spread quickly to friends and new supporters, who shined a spotlight on his situation.
Miracle on the Hudson – Dorsey calls January 15, 2009, the day Capt. Chesley B. "Sully" Sullenberger landed a failing U.S. Airways airliner on the Hudson River, a major turning point for Twitter. "It just changed everything," he said. "Suddenly the world turned its attention (to us), because we (Twitter users) were the source of news."
Sh*t My Dad Says – "Twitter celebrity" isn't exactly a career path most guidance counselors would suggest. But it happens. Justin Halpern created his "Sh*t My Dad Says" feed on August 3, 2009, to share quotes he'd collected for years. The account spawned a book deal and a TV show starring William Shatner.
The Arab Spring – The so-called "Arab Spring," which began in 2010, was fueled in part on social media like Twitter and Facebook. Young activists used the platforms to communicate among themselves and get their message out to others, even when governments sought to shut down Internet access.
The Weiner scandal – U.S. Rep. Anthony Weiner made "my Twitter was hacked" the new "dog ate my homework" in June 2011, after his account was used to send salacious selfies to a woman who was not his wife. The unfolding scandal made him the first congressman to resign over a tweet.
Loss of a legend – Perhaps it's natural that Twitter, a place first adopted by techies, would be particularly affected by the death of Apple co-founder Steve Jobs. On October 25, 2011, the day Jobs died, Twitter feeds filled with memorials, including the resurfacing of many of his quotes.
Four more years – This tweet by President Obama's account, shortly after his re-election on November 5, 2012, became the most retweeted post of all time until it was topped by Ellen DeGeneres's group selfie at the Oscars.
Vine debuts – Short messages were joined by short videos in January of this year when Twitter rolled out Vine, a mobile tool that lets users create and share looping, six-second videos. Five months later, Facebook-owned Instagram would add a similar video feature.
Lights out at the Super Bowl – Big events like awards shows and major sporting events are when Twitter is at its communal, snarky best. At its peak during the February 3 Super Bowl, thanks to a halftime performance by Beyonce and a power outage, there were 268,000 tweets being sent every minute.