Aberration correction for TEM

The transmission electron microscope (TEM) is perhaps best known for forming images at the highest resolution. It has many other capabilities, of course, forming diffraction patterns or X-ray microanalysis to name but two, but the first item to be mentioned in an instrument's specification will probably be its resolution limit. In the last few decades, the performance of the TEM has improved slowly but steadily and the resolution limit has decreased from 1 nm to around 0.2 nm. Useful progress indeed, as many interatomic distances lie in the region of 0.2 nm.