Snapchat has built a social media kingdom on the back of a fairly straightforward premise: the things you share disappear soon after you share them. Snapchat Memories, rolling out as of nowish, upends that proposition, letting you save snaps within the app for posterity. Apparently even ephemerality is ephemeral.

As Snapchat becomes the default messaging app for more people, it captures increasingly important moments.

You could previously save your own snaps to your camera roll, but keeping them within the app should make for easier curating and sharing. To access Memories, swipe up from the camera. Any snaps or stories that you've saved will be there waiting for you, searchable by date, place, or object-recognition-powered keyword. You can also edit saved snaps, or add a location, or send them to friends or intermix them with your current story (you can tell an old snap from its white frame). Have a sensitive saved snap? You can plop it in "My Eyes Only," a section that requires a PIN to access.

There are practical reasons for Memories, namely that saving snaps to your phone either leaves you vulnerable to losing that phone (and your Snapchat history along with it) or dependent on another service's cloud for backup. Since snaps are a singular form of self-documentation, might as well keep them safe on Snapchat's servers.

The more important point, though, may be that Snapchat has outgrown its original premise. As it becomes the default messaging app for more people—over two-thirds of 18-24 year olds use it, according to Comscore, along with a significant chunk of their elders—it captures increasingly important moments. A disappearing message is a fun gimmick, but some memories deserve more than that. In which case, why leave life's milestones to Instagram?

As an ancillary benefit, it should also help you live more in the moment. Take a picture or video now, save the snapping for later. That takes away some of the real-time engagement Snapchat offers, but hey, everyone's filter game should wind up that much more on point.

Yes, this is yet another process to learn as you continue your journey toward Snapchat mastery. But at least take some comfort in knowing that not even Snapchat knows exactly what it is yet.