Recent years have seen great progress in the field of cosmic magnetic fields, both in the available observational data and in the theoretical interpretations. Now we have extensive data on magnetic fields in virtually all types of cosmic objects: the Earth, the Sun, the Milky Way, out to magnetic fields in the most distant reaches of the Universe. The first detection of a magnetic field outside the Earth was made by G.E. Hale, who made optical Zeeman effect observations of magnetic fields in the Sun, nearly 100 years ago. The detection of the Zeeman effect in stars by H.W. Babcock followed some 40 years later. Optical starlight polarization observations were made in 1949 and, when combined with the DavisGreenstein effect interpretation, suggested that magnetic fields were present in our Milky Way. Radio polarization measurements confirmed this deduction in 1962.