This might take more than 140 characters to explain: Dick Costolo, Twitter’s COO, has just been named the company’s new CEO, replacing Evan Williams, who took over from Jack Dorsey just two years ago. The change signals a new period in Twitter’s development, says Business Insider. If Jack Dorsey defined Twitter and Evan Williams popularized it, Dick Costolo’s job is to make money off it. Like Dorsey before him, Evan Williams will stay on at the company in a different position. Twitter’s challenge in this third phase will be to make enough money to remain independent without alienating its users.