This has already been a pretty good year for Adele, what with the Bond theme and the new baby and all those Grammys and chart hits, but she hasn't finished racking up honors. In fact, she just added what might be her most important career milestone to date: selling more than 10 million copies of her second album, '21.'

The 10 million mark, established as the point of "diamond" certification by the RIAA, has always been out of reach for most artists, and it's only become harder to attain as record sales have dwindled over the last decade. In fact, the last release to cross 10 million was 'N Sync's 'No Strings Attached,' which earned the honor in January 2001, 43 weeks after its release.

In comparison, '21' -- which, fittingly, is the 21st album to go diamond -- took 92 weeks to get there, which is obviously quite a bit slower, but it still puts Adele in some rather rarefied company. As Billboard points out, only eight albums, among them such massive hits as 'The Bodyguard' soundtrack and Shania Twain's 'Come On Over,' have done it in less than two years.

And it's still going strong. Billboard notes that '21' moved another 28,000 copies last week, good enough for the No. 35 spot on the most recent Top 200 Albums chart. Given how thoroughly she's dominated mainstream music in 2012, it seems likely that it'll be at least a few years before we get another record out of her, but in the meantime, it seems as though the world is content to keep on buying copies of this one.