It works just as Google explained a few days ago — search results from Gmail show up in the upper right of the screen, above Google Knowledge Graph content. They're hidden from view by default, but you can click to quickly see a snapshot of your Gmail conversations relevant to the search term. Upon clicking a conversation, it brings up a dedicated view of the whole relevant email thread rather than simply moving the user into Gmail, but there's an option to click and view the messages in the native Gmail interface as well. Strangely enough, this feature doesn't appear to be supported in Safari right now, though it works fine with Chrome and Firefox. If you want to participate in the trial, you can sign up right here.
[Source: The Verge]