Which process involves the chemical alteration of the hair's structure?

The process that involves the chemical alteration of the hair's structure is perming. During perming, a chemical solution is applied to the hair, which breaks the disulfide bonds that give the hair its original shape. This alteration allows the hair to be reshaped into curls or waves as the hair is wrapped around perm rods. After the desired shape is achieved, a neutralizer is applied, which reforms the disulfide bonds in the new configuration, thus permanently changing the hair's structure.

In contrast, hair straightening can sometimes involve heat styling methods, which do not chemically alter the hair structure but rather temporarily change its shape. Coloring involves applying pigments to the hair, which does affect its properties, but it does not alter the fundamental structural bonds of the hair like perming does. Styling typically refers to arranging the hair in a particular fashion, using tools or products, and does not include any chemical processes that change the hair's architecture.