  The main aim of this paper is to introduce the most important observables
that help us to investigate stellar dynamos and compare those to the modeling
results. We give an overview of the available observational methods and data
processing techniques that are suitable for such purposes, with touching upon
examples of inadequate interpretations as well. Stellar observations are
compared to the solar data in such a way, which ensures that the measurements
are comparable in dimension, wavelength, and timescale. A brief outlook is
given to the future plans and possibilities. A thorough review of this topic
was published nearly a decade ago (Berdyugina 2005), now we focus on the
experience that have been gathered since that time.
