  More than forty years after the first detection of neutrinos from the Sun,
the spectroscopy of solar neutrinos has proven to be an on-going success story.
The long-standing puzzle about the observed solar neutrino deficit has been
resolved by the discovery of neutrino flavor oscillations. Today's experiments
have been able to solidify the standard MSW-LMA oscillation scenario by
performing precise measurements over the whole energy range of the solar
neutrino spectrum. This article reviews the enabling experimental technologies:
On the one hand mutli-kiloton-scale water Cherenkov detectors performing
measurements in the high-energy regime of the spectrum, on the other end
ultrapure liquid-scintillator detectors that allow for a low-threshold
analysis. The current experimental results on the fluxes, spectra and time
variation of the different components of the solar neutrino spectrum will be
presented, setting them in the context of both neutrino oscillation physics and
the hydrogen fusion processes embedded in the Standard Solar Model. Finally,
the physics potential of state-of-the-art detectors and a next-generation of
experiments based on novel techniques will be assessed in the context of the
most interesting open questions in solar neutrino physics: a precise
measurement of the vacuum-matter transition curve of electron-neutrino
oscillation probability that offers a definitive test of the basic MSW-LMA
scenario or the appearance of new physics; and a first detection of neutrinos
from the CNO cycle that will provide new information on solar metallicity and
stellar physics.
