Instead of defining all features in a single, large specification like CSS 2, CSS 3 is divided into several separate documents called "modules". Each module adds new capability or extends features defined in CSS 2, over preserving backward compatibility. Work on CSS level 3 started around the time of publication of the original CSS 2 recommendation. The earliest CSS 3 drafts were published in June 1999. Due to the modularization, different modules have different stability and are in different status. As of March 2011, there are over 40 CSS modules published from the CSS Working Group. Some modules such as Selectors, Namespaces, Color and Media Queries are considered stable and are either in Candidate Recommendation or Proposed Recommendation status. Once CSS 2.1 is finalized and published as Recommendation, they are likely to go to Recommendation as well. On 7 June 2011, the CSS 3 Color Module was published as a W3C Recommendation.