By default, the Tooltip property is empty. Use the ToolTip property to assign a tooltip to a column. The column's tooltip shows up when the cursor is over the header of the column. Use the CellToolTip property to assign a tooltip to a cell. The control  fires the ToolTip event when the column's tooltip is about to be displayed. The ToolTipWidth property specifies a value that indicates the width of the tooltip window, in pixels.