Neutrinos are together with photons the most abandon particles in the Universe. The
knowledge of the neutrino mass is important not only for particle physics but also for
cosmology. Oscillation experiments proved that at least two of the known three neutrino mass
states have the mass different from zero, while at least one of these states has the mass greater
than 0.05 eV. Precision spectroscopy of electrons emitted in the nuclear beta decay offers a
principal possibility to determine the neutrino mass directly in a model independent way.
However, only upper limits of the neutrino mass were determined until now. The most
advanced Karlsruhe Tritium Neutrino Mass experiment (KATRIN) operates with a
windowless gaseous source of molecular tritium. The energy of emitted electrons is analyzed
with the electrostatic retarding spectrometer with magnetic adiabatic collimation. Recently,
the first four-week science run of the KATRIN limited the neutrino mass to less than 1.1 eV.
This is twice better that the previous limit achieved after several years of measurement. The
KATRIN aims to the 0.2 neutrino mass sensitivity after 1000 days of measurements. Further
on the hypothetical sterile neutrinos in the eV and keV mass ranges will be searched for.