  The properties of neutrinos and especially their rest mass play an important
role at the intersections of cosmology, particle physics and astroparticle
physics. At present there are two complementary approaches to address this
topic in laboratory experiments. The search for neutrinoless double beta decay
probes whether neutrinos are Majorana particles and determines an effective
neutrino mass value. On the other hand experiments such as MARE, KATRIN and the
recently proposed Project 8 will investigate the spectral shape of beta-decay
electrons close to their kinematic endpoint in order to determine the neutrino
rest mass with a model-independent method. Here, because of neutrino flavour
mixing, the neutrino mass appears as an average of all neutrino mass
eigenstates contributing to the electron neutrino. The KArlsruhe TRItium
Neutrino experiment (KATRIN) is currently the experiment in the most advanced
status of commissioning. It combines an ultra-luminous molecular windowless
gaseous tritium source with an integrating high-resolution spectrometer of
MAC-E filter type. It will investigate the neutrino rest mass with 0.2 eV/c
(90% C.L.) sensitivity and allow beta spectroscopy close to the tritium
endpoint at 18.6 keV with unprecedented precision.
