Which component of hair is responsible for the texture and strength, especially when considering dark versus gray hair?

The cortex is the component of hair that is primarily responsible for its texture and strength. This middle layer contains a fibrous protein called keratin, which gives the hair its structure. The cortex is also where most of the melanin, the pigment that colors hair, is found. Variations in the cortex, such as differences in the amount and type of melanin present, account for the differences in color and texture between dark and gray hair. Gray hair typically results from a reduction in melanin production within the cortex, making it less pigmented and often coarser or different in texture compared to darker hair.