The electron microscope uses electrons to form images for this reason does not allow to observe living cells because they need to work in a high vacuum atmosphere, the samples require preparation through a long fixation process, which means that it is not possible to observe living cells. To observe a cell with this microscope, dead cells must be observed, after being fixed and stained with heavy metal ions.
In these microscopes it is not possible to observe the cells carrying out their normal behaviors (for example, migrating or dividing) under the microscope
A comparison of the three different forms of double-stranded DNA reveals that <u>Z-DNA</u> has the largest pitch per turn of the helix, whereas <u>A-DNA</u> has the widest diameter.
