The original Android M Developer Preview wasn't just a one-time release—Google promised updates. The first of those updates has been released today, called the "Android M Developer Preview 2." We're not sure what the update adds yet, but we're going to start digging. Here's Google's description:

Android M Developer Preview 2 is an incremental update to the Android M preview platform that was originally released in May 2015. The update includes a variety of enhancements and bug fixes made across the system, including those related to issues reported by developers through the external issue tracker.

The new preview version of Android M is available for download from developer.android.com, where there are updated images for the Nexus 5 Nexus 9 , and Nexus Player . The SDK has been updated as well, and for the first time ever in the Android Developer Preview program, devices that are running the old version of Android M will be sent an OTA update for the new version.

Android M was announced at Google I/O 2015 and brings user control over app permissions, a fingerprint API, a power-saving "Doze" mode, and USB type-C support. It will eventually have a new OS-wide assistant feature called "Google Now on Tap." Since it came out, we've hunted down other hidden goodies like an experimental multi-window mode, a dark theme, a revamp to the way SD cards work, and automated device backups.

Google's schedule says there should be two more releases of Android M to come. There's Dev Preview #3, the "near final" version due out in "late July," and the final SDK coming "later in Q3." Check back later for a full rundown of the changes.