Read Nice Threads (blog.twitter.com)

At Twitter, we have a history of studying how people use our service and then creating features to make what they’re doing easier. The Retweet, '@reply', and hashtag are examples of this. A few years ago we noticed people creatively stitching Tweets together to share more information or tell a longer story – like this. We saw this approach (which we call “threading”) as an innovative way to present a train of thought, made up of connected but individual elements.