Since then, Instagram has been careful to only show a few, hand-picked ads in users' feeds, for fear of alienating its fiercely loyal following - or marring the Instagram experience. But we all knew that wouldn't last.

This week, Instagram announced that it will make ads on its app "available to businesses of all types and sizes." Advertisers will also be able to target their messages to users based on their age, location and gender, as well as their interests and things they follow on Instagram.

"Working with Facebook, we will enable advertisers to reach people on Instagram based on demographics and interests, as well as information businesses have about their own customers," reads a blog post from Instagram.

To start, Instagram will open to what it calls a "select group" of Facebook marketing partners and agencies, and will expand worldwide throughout the year.