Grid tab
The Grid tab is a tab of the Chart Options dialog.
See Chart options.
Grid lines can make it easier to identify specific data points on a chart. You can display grid lines on the X or Y axes, or on both. Grid lines on the X axis run the height of the chart, at right angles to the X axis. Grid lines on the Y axis run the width of the chart, at right angles to the Y axis.
You can specify that the grid lines intersect with their axes at the major marker lines on the axis scale, at the minor marker lines, or at both, regardless of whether the marker lines are enabled on the axes.
See Scaling tab.
You can apply the same options on any secondary axes, instead of, or in addition to, the primary axes.