Users of Tumblr’s iOS and Android apps will begin to see ads in their streams – ones that look and feel like organic blog posts inside the apps.

The new ad push marks a first for Tumblr – putting sponsored content in the same context as regular posts. First reported by AdAge, users will now see as many as four of the new ads per day. You’ll be able to tell the difference between the ads and the normal posts by a dollar sign that accompanies the sponsored content.

You may recall that this dollar sign is the same way that Tumblr identified its current ads – the decidedly less-intrusive “Radar” ads that Tumblr debuted in May of last year. These ads appear on the “Spotlight” page, which highlights editor-selected blogs, as well as the Radar, which is seen on the sidebar of Tumblr pages. Back in May, the starting bid for these “Radar” ads was reported to be around $25,000.

“This mobile advertising opportunity is native to how our consumers experience content on our apps; as a continuous stream,” said Tumblr sale head Lee Brown in a statement.

Tumblr is launching the new ads with a handful of high-profile partners, including ABC Entertainment and ABC Family, GE, Pepsi, and Warner Bros. You can expect to see heavy promotion from Warner Bros, who will be serving up ads for upcoming films to the Tumblr mobile community.

This is a mobile-only push, but only for now. Tumblr confirmed to AdAge that these new types of in-stream ads will eventually pop up on the desktop version of Tumblr, but they were unwilling to give a specific date.

Tumblr recently announced that they had crossed the 100 million blogs milestone. As of now, there are over 48.6 billion posts on the site.