Characterizing pseudo oil base muds (POEM) amounts to determining the relationships between the size distribution of droplets and stability of emulsions. Conventional scanning and transmission electron microscope (SEM and TEM) have been used to investigate these problems. However, hydrated samples are difficult to handle using such techniques. The Environmental Scanning Electron Microscope (ESEM or Electroscan) and the cryogenic techniques have opened the door to the study of wet and non-conductive specimens, and of various liquids or emulsions. ESEM with the cold stage allows us to directly Visualize emulsions: without any preparation or coating; at different temperatures, by controlling the specimen temperature (between -180 degrees C and -80 degrees C) and pressure (between 400 and 1400 Pa). The purpose of this paper is to characterize pseudo oil base muds and to control: the formulation homogeneity and preparation procedure; the influence of droplet size distribution on the stability of emulsions.