In conventional SEM, the sample must be both completely dry and conductive before it can be effectively imaged. The processes used to dry samples can introduce changes in the sample. The changes introduced by preparation are well-understood, but it can sometimes be useful to view a sample in its natural state. The ESEM is designed to do this. Sample temperature and specimen chamber vapour pressure can both be controlled, allowing samples to be heated, cooled, wetted or dried. This allows dynamic experiments to be performed.

Relative humidity (RH) can be controlled within the chamber by adjusting the temperature of the conventional stage (±20° C) along with the pressure.

For example a relative humidity of 100% can be achieved by combination of low temperature (e.g. 4° C) and high water vapour pressure (e.g. 6.1 Torr).
The advantage of using 100% RH is that the sample is not being dehydrated as it is being imaged. Water can be condensed on the samples by going above 100% RH. Dynamic experiments can be performed on wet samples in real time, involving heating (on a specialised hot-stage), cooling, wetting or drying. The samples can be imaged while these dynamic processes are occurring.

Some examples of experiments that can be undertaken in the ESEM include the determination and imaging of melting dynamics for physical science materials; determination of crystallisation dynamics; and imaging of biological processes, for example pollen tube growth in real time through wetting of pollen.