Facebook can only pop so many advertisements into your News Feed before it drives you crazy.

But it needs to keep selling more and more of them to keep up its juggernaut growth. And the company is worried that it could run out of ad space in its News Feed this year.

That's probably why Facebook is now turning to some untapped real estate: its Messenger platform.

The company announced Wednesday that it's testing new ads in Messenger that look a lot like ones you might see in your News Feed.

The ads are carousel-style, meaning that users can swipe sideways through posts from several different brands within the same frame. Mercifully, they don't appear in your actual conversations (at least not yet), but rather on the platform home screen below your most recent messages and "favorite" friend column.

Facebook is currently only testing them on a "very small" group of users in Thailand and Australia.

The company also stresses that it won't use information gleaned from your private messages to target the ads, and brands can't start conversations with you unless you make the first move.

This isn't Facebook's first foray into Messenger advertising. The company rolled out an ad format last fall that allowed brands to insert conversational prompts into running chats with users. As with these new ads, advertisers are only allowed to aim them at users with whom they've communicated before.

The timing of the announcement is likely tied to Facebook's earnings report next week. The company's execs warned last year that its three-year run of explosive growth could slow down in the coming months as it maxes out ad space.