According to the gmail official blog Gmail released the New look of Gmail.The new “modern look” interface is very similar to the two Gmail preview themes released during the summer, both of which can be applied by following this guide. As promised, the new Gmail dynamically adapts to fit users’ screen sizes, as the variation of device displays continues to grow. The display density can be changed from Comfortable, to Cozy or Compact to keep novice and power-users alike content.
New Gmail Design from Carlos Jimenez on Vimeo.