Drill down allows you to get a more detailed view of the data, or somehow clarify chart element. The Manco.Chart control has special �DrillDown� event for this purposes. This event occurs when user double clicks chart element. Currently it�s supported for 2D charts only. In the drill down event handler you can load another data to the chart document and redraw chart to get a more detailed view, or show some kind of the message box, or something else.