The epidermis is the very outside layer of your skin — the part you can touch and that rubs off on a towel. It is thin, it has no blood of its own, and it is always making new cells to replace the old ones. Its quiet jobs are big: it keeps water in and dirt and germs out. Under it sits a thicker layer called the dermis, where you feel pain and where the blood is. In ordinary life people just say “skin.” You will see epidermis in biology class and on cream bottles. Though actually, it is not one even sheet: the epidermis on your palms and soles is much thicker than the skin on your eyelids, which is why a paper cut on a finger and a scratch near the eye do not feel the same.