MS Excel is not showing tree map option in chart
Solution 1:
This site says that the tree map chart is available only in Excel 2013 and 2016. This one says that it is available only in Excel 2016, but suggests that you can add it to older versions by downloading the "Tree Map App" from the Office Store.
P.S. I can confirm that it does not appear to be in Excel 2013 (for Windows).