If you check allow drilldown for a transform, double clicking a cell in the Right pane data table shows the rows in the upstream dataset that this cell/row was derived from. For example you can double click a cell in a pivot table to drilldown into the rows it was calculated from:
You can also select Drilldown... from the right click menu.
Easy Data Transform allows drilldown in the following transforms: Count, Dedupe, Ngram, Pivot and Unique.
Note that enabling drilldown slows down processing and requires more memory.
See also:
•Video: How to drilldown into data