Google has rolled out some more updates to Google Circles integration in Gmail.
When you search for an email address, Gmail would show you the information from Google Circles for that contact. You get the option to interact with that user directly from inside Gmail using chat or phone call.
Clicking on individual circles in Gmail from the sidebar would showcase the photos of the included members from their Google profiles.
You can also search circles from Gmail search by using the circle:keyword parameter.
Google spoke about these new updates:
These updates are helping us to provide a more consistent, beautiful experience across all of our products. Quick access to contact details will be rolling out to everyone today.
Of course, you would need to join Google Plus network to gain from these new features.