Except perhaps for some remote island dwellers, most people have a natural tendency to view continents as fundamental, permanent and even characteristic features of Earth. One easily forgets that the world’s continental platforms amount only to scattered and isolated masses on a planet that is largely covered by water. But when viewed from space, the correct picture of Earth becomes immediately clear. It is a blue planet. From this perspective it seems quite extraordinary that over its long history, Earth could manage to hold a small fraction of its surface always above the sea — enabling, among other things, human evolution to proceed on dry land. Is the persistence of high- standing continents just an accident? How did Earth’s complicated crust come into existence? Has it been there all the time, like some primeval icing on a planetary cake, or has it evolved through the ages? Such questions engendered debates that divided scientists for many decades, but the fascinating story of how the terrestrial surface came to take its present form is now partly resolved. That understanding shows, remarkably enough, that the conditions required to form the continents of Earth may be unmatched in the rest of the solar system.