The high-redshift galaxies became a distinct research ?eld during the ?nal decade of the20thcentury. AtthattimetheLyman-breaktechniquemadeitpossibletoidentify signi?cant samples of such objects, and the new generation of 8 to 10-m telescopes resulted in ?rst good spectroscopic data. Today the high-redshift galaxies have developed into one of the important topics of astrophysics, accounting for about 5–10% of the publications in the major scienti?c journals devoted to astronomy. Because high-redshift galaxies is a rapidly developing ?eld and since new results are published constantly, writing a book on this topic is challenging. On the other hand, in view of the large amount of individual results now in the literature, and in view of the still growing interest in this topic, it appears worthwhile to summarize and evaluate the available data and to provide an introduction for those who wish to enter this ?eld, or who, for various reasons, might be interested in its results. The end of the ?rst decade of the 21st century appears to be a good point in time to attempt such a summary. The current generation of ground-based 8 to 10-m - optical telescopes, the Hubble Space Telescope, and the most important large radio telescopes have by now been in operation since about one or two decades. Although these instruments will continue to produce important scienti?c results for some time to come, many of the initial programs exploiting their unique new possibilities have been completed.

1. The Workshop and this Tome In the excellent bucolic setting of SchloB Ringberg in Upper Bavaria, over 50 scientists assembled during the week of 23-28 September 1996 to discuss recent results, both theoretical and observational in nature, on the large scale structure of the Universe. Such a topic is perhaps nowadays far too encompassing, and is essentially all of what we used to call "observational cosmology. " The original philosophy of the organization of this meeting was deliber ated aimed at the younger community and their contributions. As a conse quence, the content of the presentations was refreshingly new, as it should be. In spite of the deficiences caused by the lack of certain key researchers in this field, for one reason or another, the final result was rewarding to all. Although the conference was held in Fall 1996, the contributions contained herein were submitted as late as Spring 1998, thus the content maintains some degree of trendiness. Originally the current volume was to be a "proceedings. " This refers to the usual archival tome that fills one's shelf and is rarely consulted, except to see the canonical group photo, which by the way, we also have. Nevertheless, I wanted something more than that. Although the field is rapidly changing, with so-called facts in a state ofconstant volubility, now is a good time for reflection prior to the commencement ofthe Sloan Survey, presumably the definitive large-scale program of low- to moderate-redshift galaxies in our lifetime.

This volume documents the theoretical and observational results and arguments in favour of (or against) the most preferred models of structure formation. New observational results of the large scale distribution of matter are confronted with recent theories on the origin and evolution of structure in the universe.

The Fourth HEIDELBERG International Conference on Dark Matter in Astro and Particle Physics, DARK2002, was held in Cape Town, South Africa, in the period 4-9 February 2002. This majestic natural area was the site of the first conference of this series (hosted since 1996 in Heidelberg) to be held outside of Germany. Dark Matter has become one of the most exciting and central fields of as trophysics, particle physics and cosmology. The conference covered, as usual for this series, a large range of topics, theoretical and experimental. Topics included Astronomical Evidence for Dark Matter, the Cosmic Microwave Background, Supersymmetry, Inflation and Dark Energy, Structure Formation, Hot and Cold Dark Matter, and Ultrahigh Energy Cosmic Rays all of which were represented by experts in the field. It was very nice to see again many of our 'old' friends in Dark Matter here in South Africa. The organizers were very glad to see, in addition to world experts, the new generation here. Many young participants gave very nice professional talks during the conference. We are grateful to John Ellis for doing an incredible job preparing his excellent summary talk during the sessions. Some special interest and intensive discussions were naturally raised by the first announcement of terrestrial evidence for hot dark matter, obtained from neutrino less double beta decay. This now adds to the evidence for cold dark matter which we have from DAM A for several years already, and which remained unchallenged up to now by other experiments.

Understanding the largest physical structures in the universe is essential for the comprehension of the cosmos as a whole. We want to know how our world is formed, what it is made of and how it evolves.Galaxies, as the most visible constituents of the universe, are interesting probes for the cosmic time sequence. Their formation and development provides us with unique clues to the cosmic evolution. This is tightly connected with the hierarchical cosmic structure: groups and clusters of galaxies and their embedding into the large scale structure offer the opportunity to study the dependencies.Galaxy redshift surveys delineate most impressively a large cosmic web, which is composed of sheets and filaments. Grand simulations of the cosmic evolution complement these observations from the theoretical side and allow one quantify and compare various model universes.Quasar absorption line studies, gravitational lensing and even the X-ray background radiation provide important quantitative measures of the history of matter clustering. Finally, the microwave radiation traces very early structures, which are supposed to originate in the phase of inflationary expansion shortly after the big bang.This volume constituting the proceedings of the 12th Potsdam Cosmology Workshop, deals with the basic aspects of cosmological structure formation on the largest physical scales.