Instagram is Snapchat now—almost, kinda, sorta.

On Tuesday, the second-most-popular social network among teenagers borrowed a major feature from the most-popular social network among teens. Instagram debuted a new functionality called “Stories” that lets users create a rolling montage of pictures and videos from the last 24 hours. Users can draw and type words on the images, swipe to add filters to them, and set which of their followers can see their own story. After displaying for a day, Stories aren’t saved like normal Instagram photos—instead, they disappear forever.

Button for button, affordance for affordance, the feature almost completely copies a Snapchat feature which is also called Stories. And Kevin Systrom, the CEO of Instagram, knows it. “They deserve all the credit,” he told TechCrunch. “This is about a format, and how you take it to a network and put your own spin on it.”

That’s a happy thought that you can only say if you employ a lot of lawyers and own an arsenal of software patents. But I digress. Stories is one of the best parts of Snapchat, which means it’s one of the best parts of the modern mobile environment. Snapchat Stories—which works so similarly to Instagram Stories that there’s no need to explain it—lets people crack jokes, point out something crazy, or post a meaningless selfie without worrying about it sticking around forever. If anything, Instagram improves on Snapchat Stories by giving it even more pride of place in the app interface: Instead of putting it in a side menu, as Snapchat does, Instagram slides it right at the top of the feed. Before you even slide down and see friends’s newest grams, you’re entreated to watch their story.

I’m honestly excited to see how my Instagram friends (who are, by and large, older than my Snapchat friends) play with a feature previously only available on the other social network. In the past 24 hours, I’ve posted stories to both Snapchat and Instagram—and maybe it’s just a fluke of my network, but my Instagram already has many more viewers.

This is about more than just a fun feature, though. As the technology researcher An Xiao Mina pointed out, Instagram Stories exist because of context collapse. Context collapse is the name of how, as our online audiences get larger, we run out of things to usefully say to them. In person, people can adjust how they speak depending on who they talk to; on the web, their potential audience could be almost anyone. Context collapse is one of the defining sicknesses of the social web today—it’s why parts of Twitter have decayed into a hyperpoliticized shoutfest, and (in my opinion) it plays into why Facebook recently started promoting content from friends over content from newspapers and other professional publishers.

So far, Instagram has managed to steer clear of the context-collapse mire. Just by being a social network composed of photos, not words, it avoids politicization in a way that Facebook and Twitter can’t. But as people and money have moved from social networks that emphasize broadcast (like Twitter, Tumblr, and Facebook) to apps that emphasize closed conversation (like WhatsApp and Snapchat), Instagram hasn’t been able to resist the tug. Two years ago, it debuted picture messaging. Stories reflects one further step, another play for conversational online usage that specifically lets users limit the audience they’re addressing. As Mina puts it, Stories lets people use Instagram closer to how most people use Snapchat—not to document the world, but to discuss it.

When the last iPhone came out, I said that it was important principally because it was a new camera. Techies might appreciate the incrementally faster processor or larger memory, but the device would improve people’s lives mostly by photographing the world more carefully and accurately than the last one did. (Obligatory reminder that the iPhone is already the best-selling camera of all time.) Instagram and Snapchat have approached that camera, and its ability to take remarkable snapshots, from two different perspectives. The former accentuates its archival capabilities, letting people construct a body of work over time that represents their lives; the latter emphasizes just how temporary and disposable its products are by actually programming their automatic disposal.

In other words, the two most popular social networks for teenagers both center on the camera—each just, so far, has constrained it differently. A month ago, Snapchat started letting people archive their snaps in a feature called Memories. With Snapchat Memories and Instagram Stories, the two most successful theses about how to use the smartphone’s camera have started to meld together. As those two apps lose their distinctiveness, I wonder if they’ll also lose what made them fun.