  Since the discovery by Hale in the early 1900s that sunspots harbor strong
magnetic field, magnetism has become increasingly important in our
understanding of processes on the Sun and in the Heliosphere. Many current and
planned instruments are capable of diagnosing magnetic field in the solar
atmosphere. Photospheric magnetometry is now well-established. However, many
challenges remain. For instance, the diagnosis of magnetic field in the
chromosphere and corona is difficult, and interpretation of measurements is
harder still. As a result only very few measurements have been made so far, yet
it is clear that if we are to understand the outer solar atmosphere we must
study the magnetic field. I will review the history of solar magnetic field
measurements, describe and discuss the three types of magnetometry, and close
with an outlook on the future.
