Excel itself does not support hierarchical data, but you can group rows and columns, and we leverage this to export hierarchies. You can do the same by setting the OutlineLevel property on rows or columns to a value greater than 0. Contiguous rows (or columns) with the same OutlineLevel value will become a group that can be expanded or collapsed. Within that group, some contiguous rows can even have a higher outline level to create a subgroup within the outer group. This can be done with up to seven levels.