Microsoft is finally closing a major gap in its Office mobile app portfolio.

Jared Spataro, general manager of Microsoft Office 365 marketing, announced on May 19 that the company has released preview versions of Word, Excel and PowerPoint for Android smartphones such as Samsung's new flagship, the Galaxy S6. Microsoft released a limited preview of Office for Android tablets last November, before opening up the early-access program to all comers just after the new year.

"The Office for Android phone apps are modern, optimized for touch and designed for work on the go," said Spataro in a statement. First, Microsoft is requiring prospective beta testers to register with the Office for Android community on Google+. Once registered, users can click on the respective Word, Excel and PowerPoint links.

Then, they wait. "Wait for ~4 hours as Google play takes time to replicate permissions, then click above mentioned links and follow the download links to install apps using Google play store," instructs the Microsoft Office for Android Google Plus page.

"Bringing these apps to Preview first provides you with an early look at the apps, while enabling us to gather critical user feedback helping us shape and improve the app experience on a wide range of Android phones across the world," Spataro said. "The feedback we received from the Office for Android tablet Preview in January was critical to ensuring a high quality and consistent Office experience across Android tablet devices."

Microsoft Office for Android phones is separate from the Office Mobile app released in 2013. Hinting that the latter's days may be numbered, "Office Mobile app for Android phone will still be available in the app store during Preview," he said. "We will disclose more about our plans for this app later in the year when we announce general availability of the new Office for Android phone app."

As in the iOS versions of the apps, a consistent user experience that transcends device type and operating system is key to Microsoft's vision of mobile-enabled productivity.

"The Office apps combine the familiar look, feel and quality of Office with a touch-friendly experience designed for Android phones," Spataro stated. "Documents open and render beautifully, with all formatting and content in the right place." Many of Office's navigational elements and options were placed within easy reach of a user's thumb, near the bottom of the screen, he added.

Embracing Google's Android ecosystem fits with Microsoft's mobile-first product strategy.

Despite a surge in the iPhone's popularity—due in no small part to the record-breaking debut of the iPhone 6 and iPhone 6 Plus—Android still dominates the smartphone scene. In February, International Data Corp. (IDC), an IT analyst group, announced that the mobile operating system had nabbed 81.5 percent of the smartphone OS market in 2014, on shipments of over 1 billion units. Apple iOS took the No. 2 spot with nearly 15 percent of the market and shipments of 192.7 million iPhones.