  After the recent experimental results on neutrino oscillations, some shape
starts to emerge from the puzzle. However, the situation is still far from
being clarified. First of all, accommodating all experimental results in a
single and simple framework is not possible, and the possibility of sterile
neutrinos entering the oscillation process has not been ruled out. Moreover,
new questions arise that the presently-available data, nor those that will be
available in a near future, will be able to answer. In this paper some of these
problems will be discussed, as well as the experimental guidelines for their
clarification.
