Towards absolute neutrino masses
  Various ways of determining the absolute neutrino masses are briefly reviewed and their sensitivities compared. The apparent tension between the announced but unconfirmed observation of the $0\nu\beta\beta$ decay and the neutrino mass upper limit based on observational cosmology is used as an example of what could happen eventually. The possibility of a ``nonstandard'' mechanism of the $0\nu\beta\beta$ decay is stressed and the ways of deciding which of the possible mechanisms is actually operational are described. The importance of the $0\nu\beta\beta$ nuclear matrix elements is discussed and their uncertainty estimated. 
Petr Vogel