Use Instagram for long enough and you'll probably rack up a few contacts that you don't really care about -- someone you followed on impulse and quickly forgot, perhaps. You might have a way to prune those unnecessary connections before long. App sleuther Jane Manchun Wong has discovered that Instagram is testing a way to group followers into categories, making them "easier to manage." You could look at the "least interacted with" crowd to unfollow a bunch of them en masse, or browse just those accounts posting artwork.
As with many tests, there's no guarantee this will be ready for widespread use in the near future, if at all. It's easy to see Instagram rolling this into a future release, though. It'll help you focus your feed on those people you care about, but it could also help on those days when you'd rather not wade through your regular feed just to find your favorites. That, in turn, could keep users coming back even if their follow lists become overwhelming.