How do you define the term 'hair cortex'?

The hair cortex is defined as the inner layer of the hair where color penetrates. It plays a significant role in determining the hair's strength, elasticity, and overall structure. This layer contains the pigment that gives hair its color, and during chemical treatments like coloring, the dye penetrates this layer to alter the hair's color. The health and condition of the cortex are critical for the overall appearance and texture of the hair, as it makes up the majority of the hair strand. Additionally, the cortex is essential for hair’s ability to hold styles and withstand environmental factors. Understanding the function of the cortex helps in making informed decisions about hair treatments and care.