We're here to celebrate and discuss scientific results from the Hubble Deep Field (Williams et al. 1997). Most would agree that this exposure represents an observational landmark in the long arduous path of exploring and understanding the Universe of faint galaxies. Indeed, it is difficult to remember a single observation in astronomy that has influenced our subject so quickly. Moreover, its full impact may not yet be realized. In this workshop, we will debate the significance of the conclusions so far derived and learn of new developments that follow directly from the HDF. This remarkable image has acted as an inspiration to many astronomers because, exceptionally, we were granted immediate access to the data. Those working with other facilities, such as ISO (Rowan-Robinson, this volume) and the VLA (Kellermann, this volume) have been quick to follow the example by concentrating their deepest exposures on this same field.
As well as explaining what I consider to be the main extragalactic highlights from the HDF at this point, largely to set the scene for the more detailed articles that follow, I will recall some of the earlier work which inserted pieces of the jigsaw that we now recognize more clearly via the HDF. Of course, HDF has also had significant impact in the non-extragalactic area. I'm glad this is well covered in the workshop but won't attempt to review progress in those important areas.