The center of this confusion is the sun's ultraviolet A (long-wave) and ultraviolet B (shortwave) rays. Our understanding of exactly what kinds of damage each causes to the skin, and how best to protect ourselves, seems to shift every year as new research comes out. For example, it was once thought that only UVB was of concern, but we keep learning more and more about the damage caused by UVA. And new, improved forms of protection against UVA keep emerging. Keeping up with these new developments is a worthwhile challenge that can help all of us prevent sun damage.