Final answer:
The stratum granulosum is the layer of the epidermis where keratinocytes undergo changes and generate proteins called keratin and keratohyalin, giving the layer a grainy appearance.
Step-by-step explanation:
The stratum granulosum is the layer of the epidermis where the keratinocytes further change as they are pushed from the stratum spinosum. In this layer, the cells become flatter, their cell membranes thicken, and they generate large amounts of proteins called keratin and keratohyalin. These proteins make up the bulk of the keratinocyte mass in the stratum granulosum and give the layer its grainy appearance.