Although solid helium was first produced over 60 years ago, by Willem H. Keesom at Leiden, it is only in the last few years that physicists have studied the surface of this solid. They have discovered that the surface has remarkable properties of great scientific interest:
▸ It is extraordinarily pure chemically, and can be made isotopically pure and free of crystal defects.
▸ Its growth is easily manipulated (as the cover of this magazine indicates) because it is more a mechanical proćess than a thermal process. In this article we examine these properties and explain the consequent unique opportunities that the helium surface gives us for studying problems that are of general interest in surface physics. Most of the findings that we discuss come from the four countries where research on the surface of solid helium is most active: the United States, the Soviet Union (see figure 1), France and Israel.