The FEI Quanta 400 ESEM has been on the market for a few years. Most operations are computer controlled. While EDS analyses are usually performed in low and high vacuum this instrument permits imaging and analysis of hydrated specimens using proprietary gaseous detectors. One need only switch to more traditional Secondary Electron (SE) Detectors (SED), Backscatter (BS) Detectors (BSD) and EDS detectors for the high vacuum work. The ESEM provides the widest universe of working and analytic conditions available for scanning electron microscopy.