How do you comprehensively analyze the chemistry of a microstructure with an SEM equipped with an energy-dispersive x-ray spectrometer (EDXS)? Prior to the 1990's there would have been perhaps two distinct and commercially available solutions to this problem. Firstly, you could have collected a number of point spectra each with a large number of counts and individually analyzed each one. The positive aspect of this, in principle, is that for each point the elemental correlations are maintained (e.g., a given point contains Al and O). The potential problem is that the region of the point analysis in question is not representative of the microstructure as a whole or subtle differences between different points could be missed. Additionally, point analyses are quite subjective and prone to missing potentially important regions of the microstructure.