Google is doing a makeover for GMail. Google began previewing a new Gmail user interface that will cut down on unnecessary clutter and and make it more beautiful and powerful.
It has adopted the clean interface from Google+.
From Google Blog:
We’re kicking things off with two new themes for you to try out as a sort of sneak peek at what we’re up to. Starting today, you’ll see the “Preview” and “Preview (Dense)” themes in the Themes tab in Gmail Settings. Why two themes? Our new interface will eventually expand dynamically to accommodate different screen sizes and user preferences, but until then you can pick the information density that you prefer.