Fortunately for us, the Messier Catalog became well known for a much higher purpose, as a collection of the most beautiful objects in the sky including nebulae, star clusters, and galaxies. It was one of the first major milestones in the history of the discovery of Deep Sky objects, as it was the first more comprehensive and more reliable list: Only four or five objects were initially missing because of data reduction errors, which could be figured out later though. Today's versions of the catalog usually include also later additions of objects observed by Charles Messier and his collegial friend, Pierre Méchain, but not included in his original list. The study of these objects by astronomers has led, and continues to lead, to important, incredible discoveries such as the life cycles of stars, the reality of galaxies as separate 'island universes,' and the possible age of the universe.