To quickly switch back and forth between the Thumbnail and the Grid View, use the Change View buttons in the center of the medium blue tool bar.
Thumbnail View, the default, displays a small representative picture and the title for each item. The Thumbnail View is good for simple browsing. Click "Grid View" to view more information about each item, such as subject, description, or date. The Grid View allows you to gather more information and easily assess relevance before viewing the full item record.
The Change View buttons are new customized enhancements to the DMR. You can still change the view option and other settings the old way, by going into "Preferences."