  The present work illustrates the potential of a new diagnostic technique that
allows the measurement of the coronal magnetic field strength in solar active
regions utilizing a handful of bright \ion[Fe x] and \ion[Fe xi] lines commonly
observed by the Hinode/EIS high-resolution spectrometer. The importance of this
new diagnostic technique lies in two basic facts: 1) the coronal magnetic field
is probably the most important quantity in coronal physics, as it is at the
heart of the processes regulating Space Weather and the properties of the solar
corona, and 2) this technique can be applied to the existing EIS archive
spanning from 2007 to 2020, including more than one full solar cycle and
covering a large number of active regions, flares, and even coronal mass
ejections. This new diagnostic technique opens the door to a whole new field of
studies, complementing the magnetic field measurements from the upcoming DKIST
and UCoMP ground based observatories, and extending our reach to active regions
observed on the disk and until now only sampled by radio measurements. In this
work we present a few examples of the application of this technique to EIS
observations taken at different times during the EIS mission, discuss its
current limitations and the steps to improve its accuracy. We also present a
list of EIS observing sequences whose data include all the lines necessary for
the application of this diagnostic technique, to help the solar community
navigate the immense set of EIS data and to find observations suitable to
measure the coronal magnetic field.
