There are several instances when it may be important to view hair under a microscope. Hair transplant applications require the use of a stereo microscope. The image below shows a hair follicle technician using a
Meiji stereo microscope to examine hair follicles.

To determine overall health of a single strand of a hair, a biological microscope can be used. The images below were captured with the
National Optical 131-CLED student microscope and a Nikon camera.

Single strand of hair at 100x magnification.

Single strand of hair at 1000x magnification. Notice the lines within the strand of hair - you can see the healthy structure of the cells. An unhealthy strand of hair would have broken bits and pieces coming off the strand of hair.