A feature that I have been following called Office 2013 Modern Authentication has now come out of private preview and is now in public preview. It is also commonly called Active Directory Authentication Library (ADAL). If you now have the Office 365 ProPlus updates from March, you have access to the capability.
Why is ADAL feature so important? It will support strong authentication natively in Office rich clients. Support for third-party solutions and smartcards has been an important request for enterprise customers. As part of this preview, there are some limitations that need to be considered. Please read the announcement here for more information - http://blogs.office.com/2015/03/23/office-2013-modern-authentication-public-preview-announced/.
In the announcement there are instructions on how to join the preview program as well there is a table that describes all the clients and operating systems that are supported.