Tree maps were intended to be visualisation aids for representing complex organisation charts, biological species, and so on. The objective of an effective controller performance visualisation chart is to present the information on the performance of the entire plant at a macro level and yet have the ability to display local (micro) details at the unit level or even the loop level. From a visual point of view it is important to provide an indication of the number of control loops in each unit rather than simply displaying them as nodes of the same size. Identifying specific control issues on a plant-wide basis and their root-causes is analogous to looking for a needle in a haystack. A relatively new technology called tree mapping may be a useful solution to this problem; it eases the visualisation challenge associated with monitoring hundreds or thousands of control assets.