1. process
2. Function
   1. Focus on only one topic
   2. Enable viewers to see the topic's details without being distracted by the rest of the map
3. How to operate?
   1. To Drill Down
      1. On the View menu,click Drill Down
      2. Click drill down icon on the toolbar
      3. Click the drill down context menu
      4. Use the shortcut key F6
      5. Choose one of these methods
   2. To Drill Up
      1. On the View menu, click Drill Up
      2. Click drill up icon on the toolbar
      3. Click drill up icon on the central topic of the drilled down map
      4. Use the shortcut Shift+F6
      5. Choose one of these methods
4. Tips
   1. Breadcrumb
      1. below the toolbar
      2. show your current map's position
   2. Note
      1. if have added floating topic(s) on the drilled down map, a drill down icon will show on the branch root topic when drill up, which means there are some details not shown on that view. You can drill down again to see them.