Twitter has announced its first social commerce addition. When Twitter hired former Ticketmaster CEO Nathan Hubbard last year to head up their “commerce team,” it became obvious they were working on something. That something is a new “Buy” button for mobile devices accessing Twitter.

Although the buttons have been appearing on and off over the summer, they’re now official as Twitter made the announcement today in a blog post. The Buy buttons are visible to a “small percentage of U.S. users,” whose numbers will grow over time.

The button allows users to do a sort of one-click buy of items seen in their Twitter timeline as sponsored posts. The entire transaction is “just a few taps,” says Twitter, and will become simpler with time. They also plan to roll it onto desktops soon.

Social shopping company Fancy is behind the current buttons, as is Gumroad and Musictoday. Most of the payments will be processed, for now, through Stripe. Initial sellers include some musicians, a few non-profits, and two retailers to include Burberry and the Home Depot.

Twitter says this is “an early step in our building functionality into Twitter to make shopping from mobile devices convenient and easy, hopefully even fun.” This indicates that there could be other social commerce rollouts coming besides this Buy button. For Twitter, it’s a win-win since it not only drives business via purchases, but it gives participants a metric to measure Twitter influence by and encourages more active use and advertising as a result.