Transmission electron microscope (TEM) gives us the highest resolution images by shining a beam of electrons directly through the sample. Contrast in the image is caused by diffraction.
Micrographs above are from very fine grained spinel sample. The diffraction pattern showing the 220, 311, 422, 511, 440 spinel lines. Very fine grain size lead a phenomena known as superplasticity.
Left micrograph shows the Mg2GeO4 spinel lamellae developed in Mg2GeO4 olivine by the Martensitic-like transformation mechanism (1600 GPa, 100°C). Right micrograph shows a group of Mg2GeO4 spinel grains nucleated on olivine/olivine grain boundary (1.9 GPa 1290 K, max stress = 973 MPa).