The mass scale of neutrinos is one of the fundamental open questions in modern physics, having implications from cosmology to particle physics. Precision measurements of the kinematics of weak decays in unstable nuclides are considered to be a model independent approach to address this question in a laboratory environment.
Nowadays two nuclides are considered to be suitable for the determination of the neutrino mass: $^3$H, which undergoes a beta decay and $^{163}$Ho which decays through electron capture. The next milestone is to reach sub-eV sensitivity with respect to the electron (anti-)neutrino mass.
Three large experiments are planned for precisely measure the endpoint region of the electron spectrum in the $^3$H beta decay: KATRIN, Project 8 and PTOLEMY and three large experiments are planned for the precise calorimetric measurement of the $^{163}$Ho electron capture spectrum: ECHo, HOLMES and NuMECS. The different techniques which have been developed by the mentioned experiments will be discussed as well as the challenges to access the sub-eV sensitivity.