How to find the source table rows used by a big complex query

We have a huge Oracle SQL query in our project which is using many views and tables for source data.

Is there any way to find the list of rows fetched from each source table by this big query when I run it?

Basically what we are trying to do is to create the bare minimum number of rows in the source tables so that the outer most big query returns at least a single record.

I have tried to run the smaller queries individually. But it is really time consuming and tedious. So I was wondering if there is a smarter way of doing this.

via Chebli Mohamed