An electron probe micro-analyzer (EPMA) is a microbeam instrument used primarily for the in situ non-destructive chemical analysis of minute solid samples. It is fundamentally the same as an Scanning Electron Microscopy (SEM), with the added capability of chemical analysis. The primary importance of an EPMA is the ability to acquire precise, quantitative elemental analyses at very small "spot" sizes (as little as 1-2 microns). The spatial scale of analysis makes it possible to analyze geological materials in situ and to resolve complex chemical variation within single grains.