The theme of protein folding is increasingly becoming a hot topic for the attention of not only biochemists, biophysicists, biotechnologists, cell and molecular biologists but also of researchers in the fields of molecular evolution and molecular medicine. Actually, protein folding has progressively revealed multi-faceted aspects linking it to two other, strictly related aspects, protein misfolding and aggregation that are being shown to be at the basis of many physiological and pathological processes.

In the past 15-20 years, all these themes have undergone profound changes of paradigms. The energy landscape theory of protein folding has provided a solid theoretical basis to interpret old experimental data and to design new experimental approaches also taking benefit of newly introduced spectroscopic and fluorescence methods. It has also exploited the singlemutant approach first introduced by Alan Fesht to assess the contribution of each single residue in the overall folding process. Presently, we can consider with confidence the possibility that in a near future we will be able to decrypt the folding code encrypted in the amino acid sequence of each polypeptide chain enabling us to propose with good approximation a threedimensional structure from any given one-dimensional string of amino acid residues under specific environmental conditions.