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.

fgspinelinsidespinellens
Micrograph of very fine grained spinel and diffraction pattern showing the 220, 311, 422, 511, 440 spinel lines. Very fine grain size lead a phenomena known as superplasticity.
martensiticlikelamellaeofspinelinolivine
Mg2GeO4 spinel lamellae developed in Mg2GeO4 olivine by the Martensitic-like transformation mechanism (1600 GPa, 100°C).
reconstructivenucleationofspinelonolivinegrainboundary
Group of Mg2GeO4 spinel grains nucleated on olivine/olivine grain boundary (1.9 GPa 1290 K (max stress = 973 MPa)).

Information on how TEM works can be found here.

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