Bionic retains a history of the changes made to your campaigns including who made the changes, date / time stamp, and the changes that were made. You can compare any 2 versions of the campaign, and restore a previous version.
Click through on the Campaign
In the upper right corner of the campaign, click on the More menu
Select View history option
You will see the full history of changes made to this campaign.
To compare 2 versions, select the respective radio buttons in the Left & Right columns.
(This is an abbreviated screenshot)
When you compare 2 versions, the system will highlight information that was either changed, removed, or added.
To restore a previous version, press the Restore This Version... link
Clicking the large Choose Versions button at the top of the page will bring back the Campaign History screen.