Why? Well, recall from physics that UV radiation is a type of electromagnetic wave and it carries more energy than normal visible light waves. And that's because it has a slightly higher frequency. So that means when UV radiation when UV rays actually hit the cells of our skin, they can end up damaging the organelles and the biological molecules such as DNA, found inside our skin cells. And that means excessive UV radiation can damage the skin and ultimately lead to things like cancer. And that's exactly why in the epidermis of our skin we have specialized cells known as melanocytes.