Google has a new UI in testing for Search on Android according to a user on Reddit. At the moment this only appears to be in testing for a small number of users, and although Google could end up introducing this new UI to the stable version of the Google app at some point in the future, the user who discovered this new UI and the visual changes that you can see in the screenshots below is using the Google app beta, specifically version 188.8.131.52, and they mention that they're on Android 6.0.1 Marshmallow, though that may not necessarily have any affect on them seeing this new UI.
The visual changes to the UI are not a drastic departure from what most people are probably seeing, but it does tend to make things seem a bit more organized and in turn should streamline the experience when searching for stuff. The more organized format takes a user's recent searches and it separates them into their own respective categories, such as images, maps, in apps, videos, news, and more. Of course there is also an "all" category as the very first tab which is what you would see first upon opening the Google app with this new UI and tapping on the search bar. This would allow users to see all of their recent searches, but should they want to narrow things down they could simply swipe or tap on one of the adjacent tabs and look for searches that are specifically of those types.
In addition to the recent searches being separated out for the tab categories that they fit under, in tabs like the one for images, you can see popular searches as well, and under the maps tab you'll see various categories like gas stations, restaurants, coffee, bars, hotels and more. What might be the most unique part of this visual change is the in apps tab which essentially just looks like your app drawer with the ability to search from within the apps that you have installed. If you're on a stock version of Android, or even on most versions of Android that have a manufacturer UI skin, a search of your apps from the app drawer is already possible, so this may seem a little bit redundant but perhaps Google wanted to make this possibility simpler and available from more places.