Dick Costolo, former Twitter CEO: a timeline

Twitter acquires Gnip, April 2014: For $134 million, Twitter buys Gnip, a provider of social data and a longstanding Twitter partner, according to the company. The idea here was to be able to collect and analyse public data so as to "[deliver] the most essential Tweets to [Twitter] partners.

Twitter stock plummets, May 2014: It was a new, and horrible low for the company's stock performance, and in the eyes of investors, evidence that Costolo was failing. Feeling the pressure then, Costolo tried to stretch or bloat the meaning of what a Twitter user is and created three representative circles, as a fascinating profile in WSJ reveals: "one circle represented the core users of the social-media service; the other denoted those who visited the site but didn't log in; and the third circle was for people who saw Twitter content embedded on other sites." Costolo wanted investors to understand that Twitter content reaches beyond Twitter users. It sort of makes sense, but it's also a bit too meta for an investor's pocketbook.

June, July 2014: Twitter scoops up Nano Media, SnappyTV, among others

Costolo had a lead foot on the gas pedal of acquisitions that summer. Twitter bought native advertising firm Nano Media to enhance its own native ad business; video startup SnappyTV to ramp up its TV-focused ad tools; and mobile retargeting and re-engagement advertising platform TapCommerce to continue building on its mobile advancements. During this time, Costolo claimed that 80% of its ad revenue came from mobile.

In an effort to bridge the gap between online promotions and offline sales, Twitter also acquired payments infrastructure company CardSpring, a company that fellow social apps like Foursquare were already using. It felt a bit random, primarily because despite catering to local businesses, Twitter is not by nature a mobile check-in app.

August 2014: Twitter launches Promoted Video

It seems that Costolo wanted to feel out the possibilities of video beyond Vine, particularly insofar as native video can better enable advertisers, brands, and publishers. Essentially, Promoted Video was yet another big, shiny ad offering that was poised to appeal to established partners.

August 2014: Taking Flight

It's just as important to attract agencies to your platform as it is to attract brands, as they're usually the ones engineering a brand's campaigns. Costolo and his team unveiled Twitter Flight School, an online resource designed to "inspire creativity and help agencies of all sizes make the most of marketing on the platform."

October 2014: Twitter launches Fabric, has first conference, and partners with IBM

Getting more pots boiling on the mobile stove, Twitter launched Fabric, a mobile platform designed to "make it easy" for developers to build apps. The product was unveiled at the company's first-ever mobile developer conference, Flight, where Costolo gave the morning keynote. Further establishing Twitter as a pioneering source of consumer data, Costolo secures a partnership with IBM to let enterprises incorporate Twitter data into their decision-making processes.

January 2015: Twitter launches group Direct Messages, and mobile video

Direct messaging has never been Twitter's forte. But, Costolo apparently did not want that to forever be the case. And so group Direct Messages was born so that users could speak with a number of fellow Tweeters privately, in one conversation. If it sounds a lot like what Facebook has done with its messenger service that's because it is.

In the very same company announcement, the ability to capture, share, and edit mobile video from the Twitter app was made available to users. Not so sure how group chat and mobile video coincide, but there it was; another cool, new feature to try.

January 2015: Twitter acquires ZipDial

Twitter acquired a Bangalore, India-based product partner, ZipDial, in a forward-thinking move. In certain countries like India, Brazil, and Indonesia, mobile is the first and foremost way people connect with the Internet. Twitter had better be there.

March 2015: Twitter launches Periscope

After acquiring Periscope in January, the company unveiled the Periscope app, one that invites users to share limited-time video content from their mobile device onto the network. It was the most exciting news to come from Twitter in some time, and a tool that both consumers and brands are still having fun figuring out.