SSRS - Representation of data in Parent child relationship

For showing the data in Parent Child relationship, we need to create grouping. Let's take an example of Product Category, Product Sub Category, Product & Order Quantity(QTY). 

Following are the steps:
1) First create a parent group for "Product Category"
2) Create a child group for "Product SubCategory" under parent group for "Product Category"
3) Create another child group for "Product" under child group for "Product SubCategory"
4) Use SUM aggregation for Order Quantity
5) We can use visibility property of Groups so that we can implement Drilldown functionality
6) In the Drill down functionality, We can see summay data for parent group and other child groups will be hidden.
7) Once we click on (+) sign then it will show data for its immediate child group.
8) Below is the screenshots:

a) Parent Child Grouping for Product Category, Product SubCategory, Product


b) Then you need to set the visibility property of child group toggled by its parent group.

c) First Parent Group

d) Second Parent Group

d) Third Level