Use the Hierarchical Options dialog box to group data hierarchically. When you group data hierarchically, you sort information based on the relationship between two fields.
This dialog box appears when you right-click in the Report Designer, point to Report, and click Hierarchical Grouping Options.
Tip It will normally be the same field that you grouped by.
The type of the Instance ID and the Parent ID must be the same.
Note The top level of the hierarchy is determined by group instances that match the Instance ID and Parent ID. If a group instance is not connected to any Parent ID, it appears at the top of the hierarchy.