to the strong interaction between electrons and matter, the specimens
have to be rather thin (<< 1000 nm) for TEM investigation.
Thus, bulk materials have to be thinned to make them electron transparent (overview).
This is done either by simply crushing them and subsequently depositing
some fragments on a carbon foil or by mechanical grinding and ion
milling. Nanoparticles of course are thin enough for direct observation.
specimens of nanotubes
are obtained in two different ways, namely either to investigate their
longitudinal or cross-sectional structure.