An SEM with a backscatter detector can be used to image changes in material. Backscatter is proportional to atomic number. A common sample to measure is the sol

An SEM with a backscatter detector can be used to image changes in material. Backscatter is proportional to atomic number. A common sample to measure is the solder diffusion depth into the copper on a pcb. The first time I imaged such a sample was mind opening in the sense of understanding why you can't remove all the solder from copper, some of the solder is in the copper.