A preview of Gmail’s new look – Official Gmail Blog

Starting June 30, 2011, you’ll see the “Preview” and “Preview (Dense)” themes in the Themes tab in Gmail Settings. Why two themes? Their 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.
Here’s what one of the new themes currently looks like:

And in conversation view:

Click the images above to see larger versions.

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