 Important investigations during the 1970s can be considered as preliminary steps for the subsequent developments. In the years 1970 the school of L. Fonda in Italy concerned with quantum decay processes and in particular with the possibility of deriving, within a quantum context, the exponential decay law (Fonda, Ghirardi, and Rimini 1978). Some features of this approach turned out to be relevant for the subsequent development of Collapse Theories: