Displaying the preview
If your device supports 3D Touch, you can use 3D Touch on a side menu content item to display the preview. On devices that do not support 3D Touch, you can use a long press on an item to preview its content.
Note: If you 3D Touch (press more deeply) an item on a side menu, you can see its preview (a peek). If you press harder, the selected item is opened (a pop).
When you 3D Touch your content from the side
, you can see a preview of the selected content. When you preview a folder, it's properties are displayed.