Biological Applications of Environmental Scanning Electron Microscopy

Abstract The environmental scanning electron microscope (ESEM) first marketed by ElectroScan and now by FEI/Philips has been recognized as the only scanning electron microscope which allows liquid water to be present in the sample chamber at temperatures above freezing. As most biological material contains a high percentage of water it would seem essential to use this technology to examine specimens in their natural state. The purpose of this presentation is to describe in detail the way in which the microscope should be used to maximize the information obtainable from a variety of biological samples. This tutorial will also consider methods which can be applied to “difficult” samples whose structure becomes altered during what would be considered a normal imaging schedule. The main features of the microscope are the use of the Peltier effect cooling stage and control of chamber water vapor pressure to enable wet specimens to be imaged.