Review of absolute neutrino mass measurements

The discovery of neutrino flavor oscillations has firmly established that at least two of the three known neutrino mass eigenstates possess a non-vanishing rest mass. Complementary to cosmology and the search for neutrino-less double beta decay laboratory-based measurements of low-energy beta decays provide a direct and model-independent approach to measure the effective electron (anti-)neutrino mass. I have reviewed the recent progress of the field starting from the first molecular tritium spectrum measured with the current state of the art KATRIN experiment before discussing the development of new approaches to achieve the sensitivity required to cover the full neutrino mass parameter range allowed in the inverted mass ordering scheme. The new avenues opened by micro-calorimeteric measurements of the electron capture decay spectrum of 163Ho (ECHo, Holmes and Numecs) and by the new technology of cyclotron radiation emission spectroscopy in combination with molecular and atomic tritium sources have been presented.