Google testing the Search Preview feature in the Google Search Results page. Without clicking the search results you can see the thumbnail of the particular results. This feature will helps you to choose the colorful page before visiting the web page.
This feature still under testing mode. Most of the time you can see the preview for popular sites only.
Set your default search engine as Google or set as your home page as Google in your browser. Then start searching in the Google home page. You will see the small lenses to show the Thumbnail of the results page.
Thanks: Google system blog