Instagram Direct is the newest feature for all iPhone and Android Instagram who download today's update.
You will now be able to send photos + videos directly from the sharing screen, to any of your followers, at a maximum of 15 people per image. Small groups can be designed for more efficient sharing.
The new feature was inspired by how pictures are being used more and more as communication (e.g. SnapChat), with Instagram Direct allowing users to directly speak to one another.
Instagram held a special conference unveiling the new feature today at 10am. Follow all the updates from the conference and read more here.