Pinterest ads are getting more pointed.

After 18 months of beta testing a self-serve platform that lets brands buy ads, Pinterest is opening the tool to all small and midsize brands in the U.S. today. We don't have a date for the U.K. launch yet, but we expect this to follow.

In addition to opening up it's ad-buying tool, Promoted Pins Ads Manager, the social site is also upping the number of interest-level targeting options from 30 to 420. Previously, brands could only buy ads based on 30 broad user interests like food, beauty and fashion. Now targeting is more specific, with marketers able to buy ads against phrases such as "healthy food," "sustainable architecture" and "street-style fashion."

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