WhatsApp Messenger has finally be updated with the most expected Material Design language in the latest update (v2.12.38). There are no new features in this update, but the Material Design refresh brings bold, colorful UI throughout the app along with new animations, icons and more. If you are using Android Lollipop, you will also see new heads up notifications on the top for messages when you are using other apps.
Facebook announced the WhatsApp acquisition in February last year that finally completed in October for $22 billion. Facebook reportedly started testing WhatsApp integration for it Android app recently. WhatsApp got calling feature recently that rolled out for all the Android users without an invite.
New WhatsApp Material Design update is not available though Google Play yet, but you can download the app from the official WhatsApp website and side-load the APK on your Android smartphone.