  In this article we summarise on-going work on the so-called Gaia FGK
Benchmark Stars. This work consists of the determination of their atmospheric
parameters and of the construction of a high-resolution spectral library. The
definition of such a set of reference stars has become crucial in the current
era of large spectroscopic surveys. Only with homogeneous and well documented
stellar parameters can one exploit these surveys consistently and understand
the structure and history of the Milky Way and therefore other of galaxies in
the Universe.
