In a regular PivotTable we can nest axis labels e.g. we can group regional data by year. Currently PowerBI only supports one level of X axis labels. There are loads of areas where this would be use...
You can nest x-axis labels in column charts! You can read more about the feature here: https://powerbi.microsoft.com/en-us/blog/power-bi-desktop-november-feature-summary/#hierarchicalAxis
