If you want to see, up-close, how your product, or hair styling device, affects the surface of the hair, or how an ingredient spreads over the hair, then you may consider doing some scanning electron microscopy (SEM).

SEM allows visualization of the hair surface at a very high level of magnification, beyond that which is possible with light microscopy.  It is ideal for helping describe hair damage effects to consumers; e.g. grooming damage, heat styling damage, split-ends, chemical damage etc.  It can also be used to investigate particulate and polymer deposition on the surface of the hair.

TRI Publications

Kamath et al (1982)