Interest in the Magellanic Clouds has grown tremendously over the past four decades. During this period they have been exposed to investigations, interpretations, and speculations with regard to their origin, evolution, structure and content. At times, they have been viewed as more spectacular than they perhaps really are, e.g. suggested to have supermassive stars and peculiar structures; at other times they have been wished far away. Shapley once said (in Galaxies, Harvard University Press, most recent edition 1973, ed. P.W. Hodge) that ‘The Astronomy of galaxies would probably have been ahead by a generation, perhaps by 50 years, if Chance, or Fate, or whatever it is that fixes things as they are had put a typical spiral and a typical elliptical galaxy in the positions now occupied by the Large and Small Magellanic Clouds…. But we must make the best of what we have, and it will soon appear that the best is indeed good. It's marvelous.’ This has indeed been shown to be true. The two irregulars, which differ in so many aspects from our Galaxy, have in particular shown their value as two excellent astrophysical laboratories near at hand.

The study of the Magellanic Clouds has in many ways become more ‘galactic’ than ‘extragalactic’. It is therefore equally impossible to cover all Magellanic Cloud research in detail in one monograph as it would be for our Galaxy.