Large-scale structures in the universe are becoming ever more important in modern astrophysics. This volume is dedicated to the memory of the late astrophysicist Fritz Zwicky and presents 34 lectures dealing with observational and theoretical aspects of the morphology of the universe. Reports on the distribution, properties and evolution of groups, clusters and superclusters of galaxies, as well as theoretical attempts to explain these findings using such ideas as biased galaxy formation and cold dark matter, are presented here for researchers and students of astronomy and astrophysics.