In the linked Google Demo Slam presentation, Pam Turley walks you through how to set up Chrome Hover Cards.

What do Hover Cards do? Have you ever had a ton of open windows and struggled to navigate back to the one you were looking for? Then hover cards may make your life a little easier. Hover Cards is a feature that gives you a thumbnail preview of each open window as you hover over the tab at the top of your Chrome browser. Watch the linked presentation to learn how!