Here's how Dick Costolo responded on Twitter moments after his resignation
Costolo will be temporarily replaced by Jack Dorsey, the CEO of Square that co-founded Twitter along with Evan Williams, Biz Stone, and Noah Glass.
Immediately after the news of his resignation hit, Costolo posted on tweet consisting of two words welcoming Dorsey back to the company.
The move comes after Twitter had been criticized for Twitter's failing to hit it's revenue and profitability targets. And, the social network's user growth seems to have stalled out.
Twitter is currently searching for a permanent CEO to replace Costolo, who joined the company in 2009 as its COO. He moved up to CEO in 2010 replacing Williams, who wanted to focus on the product.