It's certainly possible to drill down on charts.
To achieve this, set up your report's groups in the normal way, hiding each section you want to be able to drill down into.
Now when you click the Insert Chart... icon, the default will be to create the chart based on an existing group or combination of groups. Doing this will make each bar (or slice, or whatever) drillable to the group that it represents.
Be aware that you do lose some flexibility with this option, as charts can only be based on the current group or current plus next level group.
Not sure that there's an online document you can refer to, but it's not too tough to achieve.
Duncan