If you have the feeling you cannot see all items, please check the recursive flag first.
If you are using the desktop client: In the aqua main navigation window you will find a checkbox 'Recursive'. Using this, you can switch, which items should be shown. If the box is selected, you will see all items from the project, including all sub-folders. When you un-check the box, you will only see the items in the root project folder.
If you are using the web client:
In the Item Grid of the navigation window the button affects whether only the items in the selected folder are shown or whether the items of subfolders are also shown recursively.