It's common for hair to be severely damaged at the ends (think split ends) — thanks to overexposure to heat, microplastic beads in our hair-care products, and hair-coloring processes — and this breakage exposes the core of our hair to even more damage. Sound familiar?
Hair is comprised of three layers: the cuticle, cortex, and medulla. The cuticle is the hair’s outermost layer, which has shingle- or scale-like cells that work to prevent damage to the hair’s inner structure and to control the water content of hair fiber. The middle structure includes the cortex, which provides the strength, color, and texture of the hair. And the innermost structure is the medulla layer, present only in large, thick hairs.
Figure 4 in the above Scanning Electron Microscope (SEM) shows a magnified hair tip. The hair is significantly split, exposing the cortex fibers. There is also a significant amount of debris on the hair. The larger, lighter contrasting particles are microplastic beads (denoted with arrows above). The smaller, lighter contrasting particles are a combination of salts (probably from perspiration) and dead skin cells.