Work on both the graphical user interface (GUI) and the conversational user interface (CUI) started at about the same time, about 40 years ago. The GUI was a lot easier to implement, and it made computing and information resources available to ordinary people and not just to technical specialists. But over the years the GUI has lost much of its simplicity and charm. The CUI has taken many more years to develop, requiring major scientific and engineering advances in speech, natural language processing, user-modeling, and reasoning, not to mention increases in cost-effective computation. This talk surveys some of the technologies that are evolving to support natural conversation and suggests that natural conversation is what will permit simple interaction with the complex digital devices that we now encounter in our everyday lives.