1. EM samples must be dried because they are placed in a vacuum: electrons would be scattered by air or water vapour. For TEM, samples are usually dried in increasing ethanol concentrations. For SEM, critical point drying in liquid CO₂ is used, to avoid surface artefacts.
2. CLM produces clear images of lightly modified cells. However, it cannot resolve below about 100 nm. TEM provides resolution down to 1 nm, but the specimen needs to be fixed, dehydrated, and embedded to a much greater extent (i.e. more artefacts) than for CLM.