Google is adding Contacts to the side panel on Gmail. Soon, you’ll be able to learn more about the person you’re collaborating with on Gmail by hovering around the Contacts icon on the side bar. The feature has begun rolling out, but will take a couple of weeks to reach all users globally.

source https://gadgets.ndtv.com/apps/news/google-contacts-visible-gmail-sidebar-additional-information-2329940#rss-gadgets-all