Evan Williams, co-founder of Twitter is stepping down from his position as CEO of Twitter.

On the Twitter blog, Williams stated that he will stay with the company but will focus on the product side of the company. Thus he has asked Twitter COO Dick Costolo to step in as the company’s CEO.

Evan explained his reasoning in the announcement, stating:

The challenges of growing an organization so quickly are numerous. Growing big is not success, in itself. Success to us means meeting our potential as a profitable company that can retain its culture and user focus while having a positive impact on the world. This is no small task. I frequently reflect on the type of focus that is required from everyone at Twitter to get us there.

This led to a realization as we launched the new Twitter. I am most satisfied while pushing product direction. Building things is my passion, and I’ve never been more excited or optimistic about what we have to build.

This is why I have decided to ask our COO, Dick Costolo, to become Twitter’s CEO. Starting today, I’ll be completely focused on product strategy.

Internally there is little change to what will happen to Twitter, except that the CEO will be dedicating more time to the product side of twitter and the COO will step up as the CEO. Front end this will do nothing to twitter but will have the expectation that Twitter will grow more due to the dedicated focus from the co-founder.