The Library of Congress has a new kind of collection: tweets.
The library's communications director has published a blog entry giving an update on the its efforts to build a collection of tweets.
So far, it's amassed more than 170 billion tweets.
Now it's looking to make them available to the public.
The effort to build such a collection began in 20-10, when the library made an agreement with Twitter for access to all public tweets since the site's founding in 2006.
The communications director says social media is supplementing and in some cases replacing letters, journals and serial publications routinely collected by libraries.