The Incredible Sungrazing Comets

A sungrazing comet is a comet that passes extremely close to the Sun at perihelion -- sometimes within a few thousand kilometers of the Sun's surface. While small sungrazers can be completely evaporated during such a close approach to the Sun, larger sungrazers can survive many perihelion passages. However, the strong evaporation and tidal forces they experience often lead to their fragmentation.
What can these comets tell us about our solar system? Perhaps they can even reveal some of the mysteries of the sun itself...