Instagram blog:

When uploading to your feed, you’ll see a new icon to select multiple photos and videos. It’s easy to control exactly how your post will look. You can tap and hold to change the order, apply a filter to everything at once or edit one by one. These posts have a single caption and are square-only for now. On your profile grid, you’ll notice the first photo or video of your post has a little icon, which means there’s more to see.

This is a really nice update. It’s a simple change, yet easy to identity in your feed. Very nicely implemented.