deletions | additions       diff --git a/ESEM_provides_the_suitable_environment__.tex b/ESEM_provides_the_suitable_environment__.tex  index 5ee7948..53f81e6 100644  --- a/ESEM_provides_the_suitable_environment__.tex  +++ b/ESEM_provides_the_suitable_environment__.tex 
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ESEM provides the suitable environment for biological specimens in the primitive conditions, the precise spatial and temporal resolution can be achieved. The surface topology is done by ESD while the internal structures by BSE detector sometimes with the aid of fixation compounds.   The samples imaged by Collins et. al. 1993\cite{Collins_1993} were the eukaryotic  algae \textit{E. gracilis}, \textit{Spirogyra} and \textit{Saprolegnia} cells in either fully hydrated system or cryogenics states. The selected images are shown in Fig.2. In preparation of the sample, the  cells were washed by deionized water and kept in a cacodylate buffer solution of pH 7.2. The samples were then fixed in formaldehyde for several minutes and ready to be imaged. The samples were imaged with or without metal coating under different primary beam energy ($20$ or $30 KeV$) by ESD or BSE detector signals. Moreover, the thickness of the sample was less than $10\mu m$ for imaging purposes. The environment for hydrated state was maintained $3 \sim 5 \space Torr$ water vapor and $4 ^{\circ}C$.   The first observation is that the ESD images reflected the surface topology and the protein detectors and functional organs on the membranes of the cells can be clearly seen and identified. The resolution of the ESD images strongly depends upon the environment but are generally below $1 \mu m$ for $20 KeV$ primary beam. The dark and bright contrast represents the relative depth of different cells as discussed in SE sections. The limitation for ESD images is that the internal structures are obscure. The nucleus and other organelles cannot be seen by ESD images.   The second observation is that the BSE images are not clear for internal functional structures since the biological specimens mainly consist of light atoms. The